SECONDARY BATTERY, PREPARATION METHOD THEREOF, AND APPARATUS CONTAINING SAME

1 . A secondary battery, comprising an electrode plate and a tab, wherein the electrode plate comprises a current collector and an electrode plate film layer disposed on the current collector, and the electrode plate film layer has a first zone and a second zone along an extension direction of the tab, wherein the second zone is closer to the tab than the first zone, a thickness of the first zone is denoted as H1, a thickness of the second zone is denoted as H2, and the electrode plate film layer satisfies 0.6≤H2/H1<1, preferably, 0.7≤H2/H1≤0.8.

2 . The secondary battery according to claim 1 , wherein the extension direction of the tab is defined as a width direction of the electrode plate film layer, a width of the first zone is denoted as W1, a width of the second zone is denoted as W2, and the secondary battery further satisfies 0.03≤W2/W1≤0.

3 . The secondary battery according to claim 1 , wherein 0.04 mm≤H1≤0.15 mm.

4 . The secondary battery according to claim 1 , wherein 30 mm≤W1≤500 mm, preferably, 60 mm≤W1≤200 mm.

5 . The secondary battery according to claim 1 , wherein the electrode plate is a negative-electrode plate, and the negative-electrode plate comprises a negative-electrode current collector and a negative-electrode film layer disposed on the negative-electrode current collector.

6 . The secondary battery according to claim 5 , wherein the negative-electrode film layer comprises a negative-electrode active material, and the negative-electrode active material comprises a silicon-based material; preferably, the silicon-based material comprises a silicon-oxygen compound.

7 . The secondary battery according to claim 6 , wherein the mass percentage of the silicon-based material in the negative-electrode active material is ≤50%, preferably, 15%-30%.

8 . The secondary battery according to claim 5 , wherein a press density PD of the negative-electrode film layer is 1.5 g/cm 3 ≤PD≤1.8 g/cm 3 , preferably, 1.6 g/cm 3 ≤PD≤1.7 g/cm 3 .

9 . The secondary battery according to claim 1 , wherein the secondary battery comprises a positive-electrode plate, wherein the positive-electrode plate comprises a positive-electrode current collector and a positive-electrode film layer disposed on the positive-electrode current collector, the positive-electrode film layer comprises a positive-electrode active material, and the positive-electrode active material comprises a lithium transition metal composite oxide;

preferably, the positive-electrode active material comprises one or more of lithium transition metal composite oxides shown in formula 1 and modified compounds thereof;

Li a Ni b Co c M d O e A f   formula 1

in formula 1, 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from one or more of N, F, S, and Cl.

10 . A preparation method of secondary battery, comprising the following steps:

preparing an electrode plate such that the electrode plate film layer has a first zone and a second zone along an extension direction of a tab, wherein the second zone is closer to the tab than the first zone, a thickness of the first zone is denoted as H1, a thickness of the second zone is denoted as H2, and the electrode plate satisfies 0.6≤H2/H1<1.

11 . An apparatus, comprising the secondary battery according to claim 1 or a secondary battery prepared by using the method according to claim 10 .