Electrode and method for manufacturing the same
An electrode including a current collector; and an electrode active material layer disposed on at least one surface of the current collector is disclosed. The electrode active material layer includes a lower layer region facing the current collector, and an upper layer region facing the lower layer region and extended to the surface of the electrode active material layer. The lower layer region includes a first active material and a first non-rubbery binder and is free from a rubbery binder. The upper layer region includes a second active material, a second non-rubbery binder, and a rubbery binder. The rubbery binder is a hydrogenated nitrile butadiene rubber (H-NBR). Each of the first non-rubbery binder and the second non-rubbery binder includes a polyvinylidene fluoride (PVDF)-based polymer, and the weight ratio of the second non-rubbery binder to the rubbery binder in the upper layer region is 1:0.03-1:0.07.
1. An electrode comprising:
a current collector; and
an electrode active material layer disposed on at least one surface of the current collector,
wherein the electrode active material layer comprises:
a lower layer region facing the current collector, and
an upper layer region facing the lower layer region and extended to a surface of the electrode active material layer,
the lower layer region comprises a first active material and a first non-rubbery binder, and is free from a rubbery binder,
the upper layer region comprises a second active material, a second non-rubbery binder, and the rubbery binder,
the rubbery binder is a hydrogenated nitrile butadiene rubber (H-NBR),
each of the first non-rubbery binder and the second non-rubbery binder comprises a polyvinylidene fluoride (PVDF)-based polymer, and
a weight ratio of the second non-rubbery binder to the rubbery binder in the upper layer region is 1:0.03 to 1:0.07.
2. The electrode according to claim 1 , wherein a weight ratio of the lower layer region to the upper layer region is 1:1 to 1:5.
3. The electrode according to claim 1 , wherein the electrode is a positive electrode, and each of the first active material and the second active material comprises a lithium iron phosphate (LFP) compound.
4. The electrode according to claim 3 , wherein the lithium iron phosphate (LFP) compound has an average particle diameter (D50) of 0.8 μm to 2.5 μm.
5. The electrode according to claim 1 , wherein the polyvinylidene fluoride (PVDF)-based polymer comprises polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-chlorotrifluoroethylene, polyvinylidene fluoride-co-tetrafluoroethylene, polyvinylidene fluoride-co-trichloroethylene, or polyvinylidene fluoride-co-trifluoroethylene, or two or more of them.
6. The electrode according to claim 1 , wherein the weight ratio of the second non-rubbery binder to the rubbery binder in the upper layer region is 1:0.04 to 1:0.06.
7. A method for manufacturing the electrode as defined in claim 1 , comprising:
preparing a slurry for a lower layer comprising the first active material, the first non-rubbery binder, and a first dispersion medium, and free from the rubbery binder, and preparing a slurry for an upper layer comprising the second active material, the second non-rubbery binder, the rubbery binder, and a second dispersion medium;
coating the slurry for the lower layer on one surface of the current collector, and coating the slurry for the upper layer on the slurry for a lower layer, at the same time or after a predetermined time interval; and
drying the coated slurry for the lower layer and the slurry for an upper layer at the same time to form an active material layer,
wherein the rubbery binder is the hydrogenated nitrile butadiene rubber (H-NBR),
each of the first non-rubbery binder and the second non-rubbery binder comprises the polyvinylidene fluoride (PVDF)-based polymer, and
the weight ratio of the second non-rubbery binder to the rubbery binder in the slurry for an upper layer is 1:0.03 to 1:0.07.
8. The method for manufacturing the electrode according to claim 7 , wherein the electrode is a positive electrode, and each of the first active material and the second active material comprises a lithium iron phosphate (LFP) compound.
9. The method for manufacturing the electrode according to claim 8 , wherein the lithium iron phosphate (LFP) compound has an average particle diameter (D50) of 0.8 μm to 2.5 μm.
10. A lithium secondary battery comprising the electrode as defined in claim 1 as at least one of a positive electrode and a negative electrode.
11. A method for manufacturing the electrode as defined in claim 1 , comprising:
coating a slurry for a lower layer comprising the first active material, the first non-rubbery binder, and a first dispersion medium, and free from the rubbery binder on one surface of the current collector, followed by drying, to form a lower active material layer; and
coating a slurry for an upper layer comprising the second active material, the second non-rubbery binder, the rubbery binder, and a second dispersion medium on a top surface of the lower active material layer, followed by drying, to form an upper active material layer,
wherein the rubbery binder is the hydrogenated nitrile butadiene rubber (H-NBR),
each of the first non-rubbery binder and the second non-rubbery binder comprises the polyvinylidene fluoride (PVDF)-based polymer, and
the weight ratio of the second non-rubbery binder to the rubbery binder in the slurry for an upper layer is 1:0.03 to 1:0.07.
12. The method for manufacturing the electrode according to claim 11 , wherein the electrode is a positive electrode, and each of the first active material and the second active material comprises a lithium iron phosphate (LFP) compound.
13. The method for manufacturing the electrode according to claim 12 , wherein the lithium iron phosphate (LFP) compound has an average particle diameter (D50) of 0.8 μm to 2.5 μm.