Secondary battery including electrolyte additive
Disclosed is a secondary battery including an electrode assembly, which includes a cathode, an anode and a separator interposed therebetween, and an electrolyte, wherein the anode includes lithium titanium oxide (LTO) as an anode active material and the electrolyte contains a phosphate-based compound as an additive.
1. A secondary battery comprising an electrode assembly comprising a cathode, an anode and a separator interposed therebetween, and an electrolyte,
wherein the anode comprises lithium titanium oxide (LTO) as an anode active material, and
wherein the electrolyte is a gel polymer electrolyte, which contains a phosphate-based compound as an additive, wherein the phosphate-based compound comprises at least one selected from the group consisting of a pyrophosphate-based acrylate of Formula (2) and a phosphate-based urethane acrylate:
where R 1 and R 2 are each independently hydrogen, methyl or F, and n is an integer of 1 to 20.
2. The secondary battery according to claim 1 , wherein the electrolyte further contains a multifunctional compound polymerizable with the phosphate-based compound.
3. The secondary battery according to claim 2 , wherein the multifunctional compound comprises at least one selected from the group consisting of a (meth)acrylic acid ester compound, an unsaturated carbonic acid compound and a vinyl compound.
4. The secondary battery according to claim 3 , wherein the (meth)acrylic acid ester compound comprises a (meth)acrylate compound having at least two acrylate groups per molecule.
5. The secondary battery according to claim 4 , wherein the (meth)acrylate compound comprises a monomer of Formula (3) or an oligomer thereof:
where R 3 , R 4 and R 5 are each independently hydrogen, or substituted or unsubstituted C 1 -C 4 alkyl, and m is an integer of 1 to 20.
6. The secondary battery according to claim 3 , wherein the (meth)acrylic acid ester compound comprises at least one selected from the group consisting of diethylene glycol diacrylate (Di(EG)DA), diethylene glycol dimethacrylate (Di(EG)DM), ethylene glycol dimethacrylate (EGDM), dipropylene diacrylate (Di(PG)DA), dipropylene glycol dimethacrylate (Di(PG)DM), ethylene glycol divinyl ether (EGDVE), ethoxylated(6) trimethylolpropane triacrylate (ETMPTA), diethylene glycol divinyl ether (Di(EG)DVE), triethylene glycol dimethacrylate (Tri(EG)DM), dipentaerythritol pentaacrylate (DPentA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTM), propoxylated(3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated(6) trimethylolpropane triacrylate (PO(6)TMPTA), poly (ethylene glycol) diacrylate (PA1) and poly(ethylene glycol) dimethacrylate.
7. The secondary battery according to claim 1 , wherein the electrolyte contains 0.01 to 30% by weight of the phosphate-based compound based on the total weight of the electrolyte.
8. The secondary battery according to claim 2 , wherein the electrolyte contains 0.1 to 1% by weight of the multifunctional compound polymerizable with the phosphate-based compound based on the total weight of the electrolyte.
9. The secondary battery according to claim 1 , wherein the additive reacts as a crosslinking agent.
10. The secondary battery according to claim 9 , wherein the gel polymer electrolyte comprises a polymerization initiator, an electrolyte serving as a plasticizer and a lithium salt.
11. The secondary battery according to claim 10 , wherein the electrolyte contains 0.01 to 30% by weight of the lithium salt based on the total weight of solid components included in the electrolyte.
12. The secondary battery according to claim 1 , wherein the secondary battery is a lithium-ion polymer battery.
13. A method for fabricating the secondary battery according to claim 12 , the method comprising:
(a) mounting an electrode assembly in a battery case;
(b) injecting a mixture of a phosphate-based compound, a polymerization initiator, an electrolyte and a lithium salt into the battery case, followed by sealing; and
(c) polymerizing the phosphate-based compound to form a gel polymer electrolyte.
14. The method according to claim 13 , wherein the step (c) comprises:
(c1) subjecting the battery to thermal curing, photocuring via irradiation with electron beams or gamma rays, or a stabilization reaction at 30 to 80° C. to polymerize the phosphate-based compound; and
(c2) performing a formation process to activate the battery and an aging process to stabilize the activated battery.
15. A battery module comprising the secondary battery according to claim 1 as a unit cell.
16. A battery pack comprising the battery module according to claim 15 .
17. A device comprising the battery pack according to claim 16 .
18. The device according to claim 17 , wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a power storage system.