High voltage positive electrode active material including lithium manganese-based oxide and method for producing the same

Abstract

A positive electrode active material contains a lithium-rich lithium manganese-based oxide, wherein the lithium manganese-based oxide has a composition of the following chemical formula (1), and wherein a lithium ion conductive glass-ceramic solid electrolyte layer containing at least one selected from the group consisting of thio-LISICON(thio-lithium super ionic conductor), LISICON(lithium super ionic conductor), Li.sub.2S—SiS.sub.2—Li.sub.4SiO.sub.4, and Li.sub.2S—SiS.sub.2—P.sub.2S.sub.5—Lil is formed on the surface of the lithium manganese-based oxide particle:
Li.sub.1−xM.sub.yMn.sub.1−x−yO.sub.2−zQ.sub.z  (1) wherein, 0<x≤0.2, 0<y≤0.2, and 0≤z≤0.5; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Ga, In, Ru, Zn, Zr, Nb, Sn, Mo, Sr, Sb, W, Ti and Bi; and Q is at least one element selected from the group consisting of P, N, F, S and Cl.

Claims

1. A positive electrode active material comprising: lithium-rich lithium manganese-based oxide, in a form of a particle, and a lithium ion conductive glass-ceramic solid electrolyte layer formed on a surface of the particle, wherein the lithium manganese-based oxide has a composition of the following chemical formula (1),
Li.sub.1−xM.sub.yMn.sub.1−x−yO.sub.2−zQ.sub.z  (1) wherein, 0<x≤0.2, 0<y≤0.2, and 0≤z≤0.5; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Ga, In, Ru, Zn, Zr, Nb, Sn, Mo, Sr, Sb, W, Ti and Bi; and Q is at least one element selected from the group consisting of P, N, F, S and Cl, and wherein the lithium ion conductive glass-ceramic solid electrolyte layer comprises LISICON(lithium super ionic conductor), or the LISICON and at least one of thio-LISICON(thio-lithium super ionic conductor), Li.sub.2S—SiS.sub.2—Li.sub.4SiO.sub.4, or Li.sub.2S—SiS.sub.2—P.sub.2S.sub.5—Lil, and wherein the thio-LISICON is a material represented by Li.sub.1+x+y(Al, Ga).sub.x(Ti, Ge).sub.2−xSi.sub.yP.sub.3−yS.sub.12, wherein, 0≤x≤1, and 0≤y≤1, and the LISICON is a material represented by Li.sub.1+x+y(Al, Ga).sub.x(Ti, Ge).sub.2−xSi.sub.yP.sub.3−yO.sub.12, wherein, 0≤x≤1, and 0≤y≤1.

2. The positive electrode active material according to claim 1, wherein the lithium manganese-based oxide has a composition of the following chemical formula (2)
Li.sub.1+xNi.sub.aCo.sub.bMn.sub.1−x−a−bO.sub.2  (2) wherein, 0<x≤0.2, 0≤a≤0.2, 0≤b≤0.2, and 0<a+b≤0.2.

3. The positive electrode active material according to claim 1, wherein an ionic conductivity of the lithium ion conductive glass-ceramic solid electrolyte layer is 1×10.sup.−4 S.Math.cm.sup.−1 or more at room temperature.

4. The positive electrode active material according to claim 3, wherein the ionic conductivity of the lithium ion conductive glass-ceramic solid electrolyte layer is 1×10.sup.−2 S.Math.cm.sup.−1 to 1×10.sup.−3 S.Math.cm.sup.−1 at room temperature.

5. The positive electrode active material according to claim 1, wherein a content of the lithium ion conductive glass-ceramic solid electrolyte layer is 0.1 to 10% by weight, based on a total weight of the lithium manganese-based oxide.

6. The positive electrode active material according to claim 1, wherein the lithium ion conductive glass-ceramic solid electrolyte layer further includes a conductive agent.

7. A positive electrode comprising a positive electrode mixture comprising the positive electrode active material according to claim 1 formed on at least one side of a current collector.

8. A secondary battery comprising the positive electrode according to claim 7.

9. A method for producing a positive electrode active material of claim 1 comprising: (a) mixing a lithium-rich lithium manganese-based oxide powder and a lithium ion conductive glass-ceramic solid electrolyte powder containing thio-LISICON(thio-lithium super ionic conductor), LISICON(lithium super ionic conductor), Li.sub.2S—SiS.sub.2—Li.sub.4SiO.sub.4, or Li.sub.2S—SiS.sub.2—P.sub.2S.sub.5—Lil, to form a mixture; and (b) heat-treating the mixture, and the thio-LISICON is a material represented by Li.sub.1+x+y(Al, Ga).sub.x(Ti, Ge).sub.2−xSi.sub.yP.sub.3−yS.sub.12, wherein, 0≤x≤1, and 0≤y≤1, and the LISICON is a material represented by Li.sub.1+x+y(Al, Ga).sub.x(Ti, Ge).sub.2−xSi.sub.yP.sub.3−yO.sub.12, wherein, 0≤x≤1, and 0≤y≤1, wherein the heat treating is performed at 300 to 800 degrees Celsius.

10. The method for producing a positive electrode active material according to claim 9, wherein a mixing ratio of the lithium-rich lithium manganese-based oxide powder and the lithium ion conductive glass-ceramics solid electrolyte powder is 0.1 to 10% by weight based on a total weight of the lithium-rich lithium manganese-based oxide powder.

11. A method for producing a positive electrode active material according to claim 1 comprising: (i) mixing a lithium-rich lithium manganese-based oxide powder and a solid electrolyte precursor to form a mixture; and (ii) heat-treating the mixture, wherein the solid electrolyte precursor is an inorganic material including Li.sub.2O, Al.sub.2O.sub.3, Ga.sub.2O, Ga.sub.2O.sub.3, SiO.sub.2, P.sub.2O.sub.5, TiO.sub.2, GeO.sub.2, Li.sub.2S, Al.sub.2S.sub.3, GaS or Ga.sub.2S.sub.3, SiS.sub.2, P.sub.2S.sub.5, TiS or GeS.sub.2.

12. The method for producing a positive electrode active material according to claim 11, wherein a lithium compound is present on a surface of the lithium-rich lithium manganese-based oxide powder.

13. The method for producing a positive electrode active material according to claim 12, wherein the lithium compound is at least one selected from the group consisting of LiOH, Li.sub.2CO.sub.3, and Li.sub.3PO.sub.4.

14. The method for producing a positive electrode active material according to claim 11, wherein the heat treating is performed at 300 to 800 degrees Celsius.

15. A positive electrode active material comprising: lithium-rich lithium manganese-based oxide, in a form of a particle, and a lithium ion conductive glass-ceramic solid electrolyte layer formed on a surface of the particle, wherein the lithium manganese-based oxide has a composition of the following chemical formula (1),
Li.sub.1−xM.sub.yMn.sub.1−x−yO.sub.2−zQ.sub.z  (1) wherein, 0<x≤0.2, 0<y≤0.2, and 0≤z≤0.5; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Ga, In, Ru, Zn, Zr, Nb, Sn, Mo, Sr, Sb, W, Ti and Bi; and Q is at least one element selected from the group consisting of P, N, F, S and Cl, and wherein the lithium ion conductive glass-ceramic solid electrolyte layer comprises thio-LISICON(thio-lithium super ionic conductor), or the thio-LISICON and at least one of LISICON(lithium super ionic conductor), Li.sub.2S—SiS.sub.2—Li.sub.4SiO.sub.4, or Li.sub.2S—SiS.sub.2—P.sub.2S.sub.5—Lil, and wherein the thio-LISICON is a material represented by Li.sub.1+x+y(Al, Ga).sub.x(Ti, Ge).sub.2−xSi.sub.yP.sub.3−yS.sub.12, wherein, 0≤x≤1, and 0≤y≤1, and the LISICON is a material represented by Li.sub.1+x+y(Al, Ga).sub.x(Ti, Ge).sub.2−xSi.sub.yP.sub.3−yO.sub.12, wherein, 0≤x≤1, and 0≤y≤1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph illustrating ionic conductivity versus temperature of various solid electrolytes;

(2) FIG. 2 is a graph illustrating cycle characteristics of the lithium secondary batteries according to Experimental Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

EXAMPLE 1

(4) The lithium ion conductive glass-ceramic solid electrolyte composed of 30 g of Li.sub.1.15Ni.sub.0.1Co.sub.0.1Mn.sub.0.65O.sub.2 and 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12 was mixed with ZrO.sub.2 by using a ball mill for 1 hour, and the mixture was heat treated in a furnace at 650 degrees Celsius for 5 hours to produce a positive electrode active material of Li.sub.1.15Ni.sub.0.1Co.sub.0.1Mn.sub.0.65O.sub.2 coated with Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 2

(5) A positive electrode active material was produced in the same manner as in Example 1, except that the lithium ion conductive glass-ceramic solid electrolyte of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8S.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 3

(6) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.4Al.sub.0.2Ge.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 4

(7) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.4Al.sub.0.2Ge.sub.1.8Si.sub.0.2P.sub.2.8S.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 5

(8) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.4Ga.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 6

(9) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.4Ga.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8S.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 7

(10) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.4Ga.sub.0.2Ge.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 8

(11) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.4Ga.sub.0.2Ge.sub.1.8Si.sub.0.2P.sub.2.8S.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

EXAMPLE 9

(12) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of a lithium ion conductive glass-ceramic solid electrolyte of Li.sub.1.8Al.sub.0.4Ti.sub.1.6Si.sub.0.4P.sub.2.6O.sub.12 was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.o0.2P.sub.2.8O.sub.12.

COMPARATIVE EXAMPLE 1

(13) 30 g of Li.sub.1.15Ni.sub.0.1Co.sub.0.1Mn.sub.0.65O.sub.2 not coated with a solid electrolyte was prepared as a positive electrode active material.

COMPARATIVE EXAMPLE 2

(14) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of Li.sub.3PO.sub.4—Li.sub.2S—SiS.sub.2 solid electrolyte was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

COMPARATIVE EXAMPLE 3

(15) A positive electrode active material was produced in the same manner as in Example 1, except that 0.15 g of Li.sub.3.4V.sub.0.6Si.sub.0.4O.sub.4 solid electrolyte was used instead of 0.15 g of Li.sub.1.4Al.sub.0.2Ti.sub.1.8Si.sub.0.2P.sub.2.8O.sub.12.

COMPARATIVE EXAMPLE 4

(16) A positive electrode active material was produced in the same manner as in Example 1, except that Li.sub.1.15Ni.sub.0.2Co.sub.0.2Mn.sub.0.45O.sub.2 was used instead of Li.sub.1.15Ni.sub.0.1Co.sub.0.1Mn.sub.0.65O.sub.2.

EXPERIMENTAL EXAMPLE 1

(17) The positive electrode active material prepared in each of Examples 1 to 9 and Comparative Examples 1 to 3, a conductive material (Super-P) and a binder (PVdF) were mixed in a weight ratio of 96:2:2, and the mixture was added to NMP as a solvent to prepare a slurry. The slurry was then coated onto an aluminum foil in a thickness of 70 μm, dried and pressed at 130 degrees Celsius to produce a positive electrode.

(18) An artificial graphite as a negative electrode active material, an artificial graphite conductive material (Super-P) and a binder (PVdF) were mixed in a weight ratio of 95:2.5:2.5, and the mixture was added to NMP as a solvent to prepare a negative electrode mixture slurry. The slurry was then coated on a copper foil in a thickness of 70 μm, dried and pressed at 130 degrees Celsius to produce a negative electrode.

(19) Secondary batteries were manufactured by using the positive electrode and the negative electrode, a polyethylene membrane (Celgard, thickness: 20 μm) as a separator, and a liquid electrolyte in which LiPF.sub.6 was dissolved at 1 M in a mixed solvent of ethylene carbonate, dimethylene carbonate, and diethyl carbonate in a ratio of 1:2:1.

(20) 50 charge/discharge cycles were performed using the secondary batteries manufactured above under a condition of 0.5 C-rate in the range of 2.5 V to 4.6 V, and then the discharge capacity retention after 50 cycles relative to the 1 cycle discharge capacity was calculated, and the results are shown in FIG. 2 below.

(21) Referring to FIG. 2, when using the positive electrode active material according to the present invention, it can be confirmed that the lifetime characteristics are exhibited excellently.

EXPERIMENTAL EXAMPLE 2

(22) The secondary batteries manufactured in Experimental Example 1 were subjected to a rate test in a voltage range of 2.5 V to 4.6 V, and the results are shown in Table 1 below.

(23) TABLE-US-00001 TABLE 1 0.1 C./0.1 C. 0.1 C./0.2 C. 0.1 C./0.5 C. 0.1 C./1 C. vs. vs. vs. vs. 0.1 C./0.1 C. 0.1 C./0.1 C. 0.1 C./0.1 C. 0.1 C./0.1 C. Example 1 100% 94.1% 81.7% 50.8% Example 2 100% 94.7% 83.1% 53.5% Example 3 100% 94.2% 81.1% 50.5% Example 4 100% 94.0% 81.4% 51.2% Example 5 100% 93.8% 79.8% 50.3% Example 6 100% 84.0% 80.8% 53.4% Example 7 100% 93.9% 79.5% 49.8% Example 8 100% 94.2% 80.1% 51.3% Example 9 100% 95.0% 81.0% 52.5% Comparative 100% 94.0% 70.3% 36.7% Example 1 Comparative 100% 93.0% 74.9% 44.2% Example 2 Comparative 100% 93.5% 75.6% 45.4% Example 3

(24) Referring to Table 1, it can be confirmed that when the positive electrode active material according to the present invention is used, the rate characteristic is excellently exhibited. Further, referring to Comparative Examples 2 and 3, it can be confirmed that a predetermined improved rate characteristic is exhibited by coating of the solid electrolyte layer, but such an effect is slight, whereas in the case of using the solid electrolyte layer having the composition according to the present invention, a more improved effect is exhibited as compared with the case of using a solid electrolyte layer having another composition.

EXPERIMENTAL EXAMPLE 3

(25) The secondary batteries of Example 1 and Comparative Example 4 were prepared in the same manner as in

(26) Experimental Example 1, and the charge capacity and the discharge capacity were measured when the initial cycle progressed under a current condition of 0.1 C-rate in the voltage range of 2.5 V to 4.6 V, and the value calculated by (discharge capacity/charge capacity)×100 was used as 1 cycle charge and discharge efficiency. The results are shown in Table 2 below.

(27) TABLE-US-00002 TABLE 2 Charge capacity Discharge capacity (mAh/g) (mAh/g) Example 1 316.7 253.6 Comparative 258.6 204.7 Example 4

(28) Referring to Table 2 above, it can be confirmed that when the content of manganese is 0.5 or less, the capacity of the positive electrode active material having an excessive amount of manganese under a high voltage is very low and thus cannot exhibit a high-capacity characteristic, which is not suitable for the purpose of the present invention.

(29) It will be understood by those skilled in the art that various applications and modifications can be made within the scope of the present invention based on the contents described above.

INDUSTRIAL APPLICABILITY

(30) As described above, in the positive electrode active material of the present invention, by forming a solid electrolyte layer having a specific composition on the surface of lithium-rich lithium manganese-based oxide, it exhibits excellent surface stability even in a high operating voltage range of 4.5 V or more and can increase the ionic conductivity and improve the overall performance of the battery cell.