NOVEL BATTERY SYSTEMS BASED ON TWO-ADDITIVE ELECTROLYTE SYSTEMS
Improved battery systems have been developed for lithium-ion based batteries. The improved battery systems consist of two-additive mixtures in an electrolyte solvent that is a carbonate solvent, an organic solvent, a non-aqueous solvent, and/or methyl acetate. The positive electrode of the improved battery systems may be formed from lithium nickel manganese cobalt compounds, and the negative electrode of the improved battery system may be formed from natural or artificial graphite.
1 . A nonaqueous electrolyte for a lithium ion battery comprising a lithium salt, a first nonaqueous solvent, and an additive mixture comprising a first operative additive of fluoro ethylene carbonate and a second operative additive of either 1,3,2-dioxathiolane-2,2-dioxide or another sulfur-containing additive, wherein the additive mixture excludes an operative additive of 0.25% by weight or more of both tris(-trimethly-silyl)-phosphate and tris(-trimethyl-silyl)-phosphite.
2 . The nonaqueous electrolyte of claim 1 wherein a concentration of the first operative additive is in a range from 0.25 to 6% by weight.
3 . The nonaqueous electrolyte of claim 2 wherein the concentration of a second operative additive is in a range from 0.25 to 5% by weight.
4 . The nonaqueous electrolyte of claim 3 wherein the nonaqueous electrolyte does not comprise a third operative additive.
5 . The nonaqueous electrolyte of claim 4 wherein the first nonaqueous solvent is a carbonate solvent.
6 . The nonaqueous electrolyte of claim 5 further comprising a second nonaqueous solvent of methyl acetate.
7 . The nonaqueous electrolyte of claim 6 wherein the second operative additive is 1,3,2-dioxathiolane-2,2-dioxide.
8 . The nonaqueous electrolyte of claim 3 further comprising a second nonaqueous solvent of methyl acetate.
9 . A lithium-ion battery comprising:
a negative electrode;
a positive electrode; and
a nonaqueous electrolyte comprising lithium ions dissolved in a first nonaqueous solvent, and an additive mixture comprising:
a first operative additive of either fluoro ethylene carbonate;
a second operative additive of either 1,3,2-dioxathiolane-2,2-dioxide or another sulfur-containing additive; and
excluding an operative additive of 0.25% by weight or more of tris(-trimethly-silyl)-phosphate and tris(-trimethyl-silyl)-phosphite.
10 . The lithium-ion battery of claim 9 wherein a concentration of the first operative additive is in a range from 0.25 to 6% by weight.
11 . The lithium-ion battery of claim 10 wherein a concentration of the second operative additive is in a range from 0.25 to 6% by weight.
12 . The lithium-ion battery of claim 11 wherein the nonaqueous electrolyte does not comprise a third operative additive.
13 . The lithium-ion battery of claim 12 wherein the first nonaqueous solvent is a carbonate solvent.
14 . The lithium-ion battery of claim 13 further comprising a second nonaqueous solvent of methyl acetate.
15 . The lithium-ion battery of claim 14 wherein the positive electrode comprises either NMC532 or NMC622, with a grain size of greater than 0.5 micrometers.
16 . The lithium-ion battery of claim 15 wherein the positive electrode is coated with aluminum oxide or titanium dioxide.
17 . The lithium-ion battery of claim 11 further comprising a second nonaqueous solvent of methyl acetate.
18 . An electric vehicle with a rechargeable battery comprising:
a drive motor;
gear box;
electronics; and
a battery system comprising:
a negative electrode;
a positive electrode; and
a nonaqueous electrolyte comprising:
lithium ions;
a first nonaqueous solvent comprising a carbonate solvent;
a second nonaquaeous solvent comprising methyl acetate;
and an additive mixture of a first operative additive of either vinylene carbonate or fluoro ethylene carbonate and a second operative additive of either 1,3,2-dioxathiolane-2,2-dioxide or another sulfur-containing additive.
19 . The electric vehicle of claim 18 wherein the positive electrode comprises either NMC532 or NMC622, with a grain size of greater than 0.5 micrometers.
20 . The electric vehicle of claim 19 wherein the battery system has 95% retention of initial capacity after 200 cycles between 3.0 V and 4.3 V at a charging rate of C/3 CCCV at 40° C.