Non-aqueous electrolytic solution with mixed salts
View Patent ↗The use of at least two electrolyte salts in a lithium secondary battery provides improved battery performance such as long cycle life of high discharge capacity and high capacity retention.
1. A secondary battery comprising:
a. an anode
b. a cathode, and,
c. an electrolytic solution, comprising
i. a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene carbonate and ethylmethyl carbonate in a volume ratio of about 1:4 to about 1:1,
ii. a first salt comprising lithium bis(oxalato)borate in a concentration of greater than 0.15 M to about 2.0 M and
iii. a second salt in a concentration of about 0.1 M to about 1.6 M, wherein the second salt is selected from the group consisting of LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiTaF 6 , LiAlCl 4 , Li 2 B 10 Cl 10 , LiCF 3 SO 3 , LiE(C n F 2n+1 SO 2 ) m , wherein m=2 or 3, wherein E=N when m=2, and wherein E=C when m=3, and n=1–10; LiPF x (R F ) 6−x , and LiBF y (R F ) 4−y , wherein R F represents perfluorinated C 1 –C 20 alkyl groups or perfluorinated aromatic groups, x=0–5, and y=0–3, and combinations thereof.
2. The secondary battery of claim 1 wherein the cathode comprises a lithium mixed metal oxide selected from the group consisting of LiMnO 2 , LiMn 2 O 4 , LiCoO 2 , Li 2 Cr 2 O 7 , Li 2 CrO 4 , LiNiO 2 , LiFeO 2 , LiNi x Co 1−x O 2 (0<x<1), LiFePO 4 , LiMn 0.5 Ni 0.5 O 2 , LiMn 1/3 Co 1/3 Ni 1/3 O 2 , and LiMc 0.5 Mn 1.5 O 4 wherein Mc is a divalent metal, and mixtures thereof.
3. The secondary battery of claim 1 wherein the cathode further comprises a binder selected from the group consisting of polyvinylidene fluoride, styrene-butadiene rubber, polyamide, melamine, and combinations thereof.
4. The secondary battery of claim 1 wherein the anode comprises a material selected from the group consisting of crystalline carbon, lithium metal, LiMnO 2 , LiAl, LiZn, Li 3 Bi, Li 3 Cd, Li 3 Sd, Li 4 Si, Li 4.4 Pb, Li 4.4 Sn, LiC 6 , Li 3 FeN 2 , Li 2.6 Co 0.4 N, Li 2.6 Cu 0.4 N, Li 4 Ti 5 O 12 , and combinations thereof.
5. The secondary battery of claim 1 wherein the anode further comprises a binder selected from the group consisting of polyvinylidene fluoride, styrene-butadiene rubber, polyamide, melamine, and combinations thereof.
6. The secondary battery of claim 1 wherein the second salt is selected from the group consisting of LiPF 6 , LiBF 4 , and combinations thereof.
7. The secondary battery of claim 1 wherein lithium bis(oxalato)borate is present in a concentration of greater than 0.3 M to about 1.6 M.
8. The secondary battery of claim 1 wherein lithium bis(oxalato)borate is present in a concentration of about 0.4 M to about 1.2 M.