Continuous manufacturing method of lithium rechargeable battery forming passive film on surface of lithium metal electrode and lithium rechargeable battery manufactured therefrom

Abstract

The present invention provides a manufacturing method of a lithium rechargeable battery, including (i) preparing a lithium metal electrode in which metal lithium (Li) is formed on one surface or both surfaces of a current collector; (ii) applying an electrolyte solution for coating including one or more lithium salts, one or more non-aqueous organic solvents, and one or more additives on a surface of the metal lithium to form a passive film which is a stable coat; (iii) manufacturing an electrode assembly including the lithium metal electrode as a negative electrode; and (iv) housing the electrode assembly in a rechargeable battery case and injecting an electrolyte solution for injection including one or more lithium salts, one or more non-aqueous organic solvents, and one or more additives to manufacture a rechargeable battery.

Claims

1. A method of manufacturing a lithium rechargeable battery, comprising: (i) preparing a lithium metal electrode in which lithium metal (Li) is formed on one surface or both surfaces of a current collector; (ii) applying an electrolyte coating solution on a surface of the lithium metal without applying any electric potential to form a passive film which is a stable coat, where the electrolyte coating solution includes one or more lithium salts for coating, one or more non-aqueous organic solvents for coating, and additives for coating; (iii) manufacturing an electrode assembly including the lithium metal electrode having the passive film formed thereon as a negative electrode; and (iv) housing the electrode assembly in a rechargeable battery case and injecting an electrolyte injection solution to manufacture a rechargeable battery, where the electrolyte injection solution includes one or more lithium salts for injection, one or more non-aqueous organic solvents for injection, and one or more additives for injection; wherein: the additives for coating cause a reductive decomposition reaction at the higher potential than the non-aqueous organic solvents for coating, and comprise fluoroethylene carbonate (FEC), and one or more selected from the group consisting of vinylene carbonate (VC), propane sultone (PS), 1,3-propane sultone (PRS), succinonitrile (SN), adiponitrile (AN), hexane tricarbonitrile (HTCN), and gamma-butyrolactone (GBL), the additives for injection comprise one or more selected from the group consisting of pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivatives, sulfur, a quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, carbon tetrachloride, trifluoroethylene, fluoroethylene carbonate (FEC), and propane sultone (PS), and an additive composition consisting of the additives for coating is different from an additive composition consisting of the additives for injection.

2. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive composition consisting of the additives for coating comprises one or more different additives from the additives included in the additive composition consisting of the additives for injection, or an amount of one or more of the additives included in the additive composition consisting of the additives for coating is different from an amount of one or more of the additives included in the additive composition consisting of the additives for injection.

3. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the current collector comprises a copper foil.

4. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the lithium metal is formed on the one surface or both surfaces of the current collector by deposition or rolling.

5. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for coating comprises vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

6. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for coating is included in the electrolyte solution for coating at 0.1 to 20 wt %, based on a total weight of the electrolyte solution for coating.

7. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the applying of the electrolyte coating solution is performed by dip coating or roll to roll coating.

8. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the applying of the electrolyte coating solution is performed at least once.

9. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the passive film comprises a solid electrolyte interphase (SEI) coat.

10. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the electrode assembly includes a negative electrode which is the lithium metal electrode having the passive film formed thereon, a positive electrode, and a separator interposed between the negative electrode and the positive electrode.

11. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for injection is one or more selected from the group consisting of fluoroethylene carbonate (FEC) and propane sultone (PS).

12. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for injection is included in the electrolyte injection solution in an amount of 0.1 to 10 wt %, based on a total weight of the electrolyte injection solution.

13. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the lithium metal electrode is continuously manufactured in a sheet form.

14. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for coating is included in the electrolyte coating solution in an amount of at 0.5 to 10 wt %, based on a total weight of the electrolyte injection solution.

15. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for coating is included in the electrolyte coating solution in an amount of at 1 to 5 wt %, based on a total weight of the electrolyte injection solution.

16. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for injection is included in the electrolyte injection solution in an amount of at 0.5 to 7 wt %, based on a total weight of the electrolyte injection solution.

17. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the additive for injection is included in the electrolyte injection solution in an amount of at 0.5 to 5 wt %, based on a total weight of the electrolyte injection solution.

18. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the lithium salts for coating and the lithium salts for injection independently comprise one or more selected from the group consisting of LiCl, LiBr, LiI, LiClO.sub.4, LiBF.sub.4, LiB.sub.10Cl.sub.10, LiPF.sub.6, LiCF.sub.3SO.sub.3, LiCF.sub.3CO.sub.2, LiAsF.sub.6, Li SbF.sub.6, LiAlCl.sub.4, CH.sub.3SO.sub.3Li, CF.sub.3SO.sub.3Li, (CF.sub.3SO.sub.2).sub.2NLi, chloroborane lithium, aliphatic lithium carbonate, lithium 4-phenyl borate, and imide.

19. The method of manufacturing a lithium rechargeable battery of claim 1, wherein the non-aqueous organic solvent for coating and the non-aqueous organic solvent for injection independently comprise one or more selected from the group consisting of aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyro lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, formic acid methyl, acetic acidmethyl, phosphoric acid triester, trimethoxy methane, a dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, a propylene carbonate derivative, a tetrahydrofuran derivative, ether, methyl propionate, and ethyl propionate.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a method of applying an electrolyte solution for coating according to an exemplary embodiment of the present invention.

(2) FIG. 2 is a schematic view of a method of applying an electrolyte solution for coating according to another exemplary embodiment of the present invention.

MODE FOR INVENTION

(3) Hereinafter, the present invention will be described referring to the Examples according to the present invention, which is however for better understanding of the present invention, and the scope of the present invention is not limited thereto.

Example 1

(4) Metal lithium (thickness: 20 μm) was rolled on a current collector (thickness: 10 μm) composed of copper to manufacture a lithium metal negative electrode sheet. The lithium metal negative electrode sheet was soaked in an electrolyte solution for coating by the method shown in FIG. 1 to form a passive film on the surface. Here, as the composition of the electrolyte solution for coating, a liquid electrolyte solution of 1 M LiPF.sub.6 dissolved in a mixed solvent of ethylene carbonate, dimethylene carbonate, diethyl carbonate at 1:2:1 including FEC and VC as an additive at 10 wt % and 2 wt %, respectively was used.

(5) The lithium metal negative electrode was stamped and used as the negative electrode.

(6) A Co precursor and Li.sub.2CO.sub.3 were mixed and sintered in a furnace at a temperature of 940° C. for 10 hours to prepare LiCoO.sub.2 which was used as a positive electrode active material, and PVdF as a binder and Super-P as a conductive material were used. The positive electrode active material, the binder, and the conductive material were mixed well in NMP so that the weight ratio is 95:2.5:2.5, and the mixture was applied (a loading amount: 4 mAh/cm.sup.2) on an Al foil having a thickness of 12 μm, dried at 130° C., and rolled so that an electrode porosity is 30%, thereby manufacturing a positive electrode.

(7) The positive electrode, the negative electrode, a polyethylene film (Celgard, thickness: 12 μm) as a separator, and a liquid electrolyte solution of 1 M LiPF.sub.6 dissolved in a mixed solvent of ethylene carbonate, dimethylene carbonate, and diethyl carbonate at 1:2:1 including FEC and PS as an additive at 5 wt % and 2 wt %, respectively as an electrolyte solution for injection were used, and housed in a pouch type case, thereby manufacturing rechargeable batteries.

Example 2

(8) The lithium rechargeable battery was manufactured in the same manner as in Example 1, except that the passive film was formed on the lithium metal negative electrode sheet by the method shown in FIG. 2, and as the composition of the electrolyte solution for coating, a liquid electrolyte solution of 1 M LiPF.sub.6 dissolved in a mixed solvent of ethylene carbonate, dimethylene carbonate, and diethyl carbonate at 1:2:1 including FEC and VC as an additive at 10 wt % and 2 wt %, respectively was used.

Comparative Example 1

(9) The lithium rechargeable battery was manufactured in the same manner as in Example 1, except that the lithium metal sheet having no passive film formed thereon was stamped and used as the negative electrode.

Comparative Example 2

(10) The lithium rechargeable battery was manufactured in the same manner as in Example 1, except that as the composition of the electrolyte solution for injection, a liquid electrolyte solution of 1 M LiPF.sub.6 dissolved in a mixed solvent of ethylene carbonate, dimethylene carbonate, and diethyl carbonate at 1:2:1 without an additive was used.

Comparative Example 3

(11) The lithium rechargeable battery was manufactured in the same manner as in Example 1, except that the lithium metal sheet having no passive film formed thereon was stamped and used as the negative electrode, and as the electrolyte solution for injection, a liquid electrolyte solution of 1 M LiPF.sub.6 dissolved in a mixed solvent of ethylene carbonate, dimethylene carbonate, and diethyl carbonate at 1:2:1 including FEC, VC, and PS as an additive at 10 wt %, 2 wt %, and 2 wt %, respectively was used.

Comparative Example 4

(12) The lithium rechargeable battery was manufactured in the same manner as in Example 1, except that as the composition of the electrolyte solution for injection, a liquid electrolyte solution of 1 M LiPF.sub.6 dissolved in a mixed solvent of ethylene carbonate, dimethylene carbonate, and diethyl carbonate at 1:2:1 including VC as an additive at 2 wt % was used.

Experimental Example 1

(13) The rechargeable batteries manufactured according to Examples 1 and 2 and Comparative Example 1 were charged and discharged twice at 0.2 C in a range of 3 V-4.3 V, thereby measuring an initial discharge capacity and discharge efficiency, and the results are shown in the following Table 1. Thereafter, charge at 0.1 C and discharge at 0.5 C were performed 100 times and a discharge capacity for 100 times relative to a discharge capacity for once and a retention ratio were calculated, and the results are shown in the following Table 1.

(14) TABLE-US-00001 TABLE 1 Discharge capacity/ discharge efficiency 100 times (%) Example 1 1174 mAh, 99.95% 1033 mAh (87%) Example 2 1172 mAh, 99.94% 1020 mAh (87%) Comparative Example 1 1178 mAh, 99.88%  233 mAh (20%) Comparative Example 2 1174 mAh, 99.93%  0 mAh (0%)

(15) Referring to Table 1, it was confirmed that the lithium rechargeable battery manufactured by forming the passive film on the lithium metal electrode according to the present invention suppressed non-uniform production and growth of a lithium dendrite, and thus, improved charge and discharge efficiency, thereby improving a life characteristic of a battery, while the lithium rechargeable battery which had no passive film previously formed thereon or the lithium rechargeable battery which had the passive film formed thereon but used no additive in the electrolyte solution for injection had a significantly reduced life characteristic.

Experimental Example 2

(16) The rechargeable batteries manufactured according to Examples 1 and 2 and Comparative Examples 2 to 4 were charged and discharged at 0.2 C in a range of 3 V-4.3 V and the capacities were confirmed, and then the rechargeable batteries were recharged at 0.2 C to 4.3 V and left at a temperature of 60° C. for 21 days. The thicknesses and the swelling ratios were measured and the results are shown in the following Table 2.

(17) TABLE-US-00002 TABLE 2 Initial Thickness Swelling thickness after 21 days ratio (mm) (mm) (%) Example 1 2.78 2.96 6.5 Example 2 2.77 2.97 7.2 Comparative Example 3 2.79 3.27 17.2 Comparative Example 4 2.77 3.58 29.2

(18) Referring to Table 2, it was confirmed that in the Examples in which the passive film was formed using an additive allowing the characteristics of the passive film to be excellent and then the additive is not included in the electrolyte solution for injection, a swelling problem which may cause a problem during high temperature storage of the lithium rechargeable battery was solved, while in Comparative Examples 3 and 4 in which the additive such as VC for forming the passive film having excellent properties is included in the electrolyte solution for injection, the swelling problem during high temperature storage was serious due to gas production by a residual amount of additive.

(19) A person having ordinary knowledge in the art to which the present invention pertains may conduct various applications and modifications within the scope of the present invention, based on the above descriptions.

INDUSTRIAL APPLICABILITY

(20) As described above, the manufacturing method of a lithium rechargeable battery according to the present invention includes first applying an electrolyte solution for coating including an additive advantageous for the characteristics of the passive film on a lithium metal electrode to form the passive film, before assembling an electrode assembly and the lithium rechargeable battery, and using the lithium metal electrode having the passive film formed thereon to manufacture the electrode assembly and the lithium rechargeable battery, thereby capable of forming the uniform passive film on a surface of the lithium metal electrode. Thus, non-uniform production and growth of the lithium dendrite of the manufactured lithium rechargeable battery are suppressed, and accordingly, charge and discharge efficiency is improved, thereby having an effect of contributing to improvement of a battery life.

(21) Moreover, the additive which may cause a problem during operation of the lithium rechargeable battery is not included in the electrolyte solution for injection, thereby preventing degradation of lithium rechargeable battery performance.