Positive electrode piece in a battery, electrochemical device and apparatus
The present application relates to the field of battery, in particular to a positive electrode piece, an electrochemical device and an apparatus. The positive electrode piece of the present application includes a current collector and an electrode active material layer arranged on at least one surface of the current collector, where the current collector includes a support layer and a conductive layer arranged on at least one surface of the support layer. The thickness D2 of one side of the conductive layer D2 satisfies 30 nm≤D2≤3 μm, the material of the conductive layer is aluminum or aluminum alloy, and the density of the conductive layer is 2.5 g/cm 3 to 2.8 g/cm 3 , and a primer layer containing a conductive material and a binder is also arranged between the current collector and the electrode active material layer.
1. A positive electrode piece, comprising:
a current collector, wherein the current collector comprises a support layer and a conductive layer disposed on at least one surface of the support layer, wherein
a single side thickness D2 of the conductive layer satisfies 30 nm≤D2≤3 μm,
a material of the conductive layer is aluminum or aluminum alloy,
a volume resistivity of the conductive layer is 2.7×10 −8 Ω·m to 5.×10 −8 Ω·m, and
a density of the conductive layer is 2.5 g/cm 3 to 2.8g/cm 3 , and
a material of the support layer is selected from at least one of a conductive polymer material and a conductive polymer composite material, from a direction of a width of a coated surface of the positive electrode piece;
the support layer has a Young's modulus (E) at room temperature of 4 GPa≤E≤20 GPa;
an electrode active material layer disposed on at least one surface of the current collector, wherein
the electrode active material layer comprises three regions extending in a winding direction of the positive electrode piece, the three regions comprising a middle region and two side regions in the direction of the width, wherein the two side regions have a first compaction density and the middle region has a second compaction density, wherein the first compaction density is at least 4% lower than the second compaction density, wherein the direction of the width is perpendicular to the winding direction of the positive electrode piece; and
a primer layer comprising a conductive material and a binder, wherein the primer layer is arranged between the current collector and the electrode active material layer, wherein
the conductive material is a conductive carbon material, and the conductive carbon material is selected from at least one of zero-dimensional conductive carbon material, one-dimensional conductive carbon material, two-dimensional conductive carbon material and three-dimensional conductive carbon material, wherein
when the conductive carbon material comprises the one-dimensional conductive carbon material and the two-dimensional conductive carbon material, the one-dimensional conductive carbon material and the two-dimensional conductive carbon material account for 1 wt % to 50 wt % of the conductive material.
2. The positive electrode piece according to claim 1 , wherein the single side thickness D2 of the conductive layer satisfies 300 nm≤D2≤2 μm.
3. The positive electrode piece according to claim 1 , wherein a surface of the conductive layer is also provided with a protective layer, the protective layer is only arranged on one surface or both surfaces of the conductive layer of the current collector; and a thickness of the protective layer D3 satisfies D3≤1/10D2 and 1 nm≤D3≤200 nm.
4. The positive electrode piece according to claim 1 , wherein the protective layer is a metal protective layer or a metal oxide protective layer; and the conductive layer comprises an upper protective layer and a lower protective layer, and a thickness of the upper protective layer is D a , 1 nm≤D a ≤200 nm and D a ≤0.1D1; and a thickness of the lower protective layer is D b , 1 nm≤D b ≤200 nm and D b ≤0.1D1; D a >D b ; and both the upper protective layer and the lower protective layer are metal oxide protective layers.
5. The positive electrode piece according to claim 1 , wherein, based on the total weight of the primer layer, a weight percentage content of the binder is 30% to 99%; and/or, based on the total weight of the primer layer, a weight percentage content of the conductive material is 1% to 70%.
6. The positive electrode piece according to claim 1 , wherein the binder is selected from at least one of styrenebutadiene rubber, oil soluble polyvinylidene fluoride (PVDF), PVDF-HFP copolymers, PVDF-TFE copolymers, sodium carboxymethyl cellulose, polystyrene, polyacrylic acid, polytetrafluoroethylene, polyacrylonitrile, polyimide, water soluble PVDF, polyurethane, polyvinyl alcohol, polyacrylate, polyacrylic acid-polyacrylonitrile copolymer, and polyacrylate-polyacrylonitrile copolymer.
7. The positive electrode piece according to claim 1 , wherein a thickness of the primer layer H is 0.1 μm to 5 μm.
8. The positive electrode piece according to claim 1 , wherein the electrode active material layer comprises an electrode active material, a binder and a conductive agent.
9. An electrochemical device, comprising a positive electrode piece, a negative electrode piece, an isolation membrane and electrolyte, wherein the positive electrode piece is the positive electrode piece according to claim 1 .
10. An apparatus, comprising the electrochemical device of claim 9 .
11. The positive electrode piece according to claim 1 , wherein the first compaction density is 5% to 30% lower than the second compaction density.
12. The positive electrode piece according to claim 1 , wherein the middle region has an area 20% to 80% of a total area of the middle region and the two side regions.
13. The positive electrode piece according to claim 1 , wherein the support layer has a thermal shrinkage at 90° C. not more than 1.5%.
14. The positive electrode piece according to claim 1 , wherein the support layer has an elongation at break less than less than 400%.