Negative electrode sheet and preparation method thereof, secondary battery and power-consuming device

Abstract

The present application proposes a negative electrode plate and its preparation method, a secondary battery and an electrical device; the preparation method includes coating a first slurry and a second slurry on the same side in the height direction of the negative electrode current collector to form a first negative electrode layer and a second negative electrode layer; the second negative electrode layer is located on both sides of the first negative electrode layer in the width direction of the first negative electrode layer and the surface capacity of the first negative electrode layer is greater than that of the second negative electrode layer; the thickness of the second negative electrode layer in the height direction of the negative electrode current collector is less than that of the first negative electrode layer; after rolling, the thickness of the second negative electrode layer is equal to the thickness of the first negative electrode layer and the compaction density of the second negative electrode layer is ρ2, and the compaction density of the first negative electrode layer is ρ1; ρ2=ρ1×(1-k1); k1 is 1%-5%. The negative electrode plate obtained by this preparation method expands less during charging and discharging. The present application also proposes a secondary battery and an electrical device so that the entire interface contact is good during charging and discharging of the battery cell, and the battery cell cycle performance is excellent.

Claims

1. A method for preparing a negative electrode sheet, characterized in that: The steps include: preparing a first slurry and a second slurry; A first slurry and a second slurry are respectively applied on the same side of the negative electrode current collector in the height direction to form a first negative electrode layer and a second negative electrode layer; the second negative electrode layer is located on both sides of the first negative electrode layer in the width direction of the first negative electrode layer, and the surface capacity of the first negative electrode layer is greater than that of the second negative electrode layer; the thickness of the second negative electrode layer is less than that of the first negative electrode layer in the height direction of the negative electrode current collector; Roll pressing, before rolling, the thickness of the second negative electrode layer in the height direction of the negative electrode current collector is H2, the thickness of the first negative electrode layer is H1, H2=H1×(1-k2); wherein k2 is 1%-5%; after rolling, the thickness of the second negative electrode layer is equal to the thickness of the first negative electrode layer, and the compaction density of the second negative electrode layer after rolling is ρ2, and the compaction density of the first negative electrode layer after rolling is ρ1; ρ2=ρ1×(1-k1); wherein k1 is 1%-5%.

2. The preparation method according to claim 1, characterized in that In the width direction of the first negative electrode layer, the second negative electrode layer is symmetrically arranged on both sides of the first negative electrode layer; before rolling, the width of the second negative electrode layer on either side is L2, the width of the first negative electrode layer is L1, and L2 / L1=1%-5%.

3. The preparation method according to claim 1, characterized in that Based on the first slurry, it includes 90-98 wt% of the first negative electrode active material, 0.5-5 wt% of the first conductive agent, and 0.5-5 wt% of the first binder; And / or, the first negative electrode active material includes at least one of natural graphite, artificial graphite, and silicon-based materials; and / or, the first conductive agent comprises at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, carbon nanotubes, graphene, metal powder or carbon fiber; And / or, the first binder includes at least one of styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polyvinyl alcohol, and polyvinylidene fluoride.

4. The preparation method according to claim 1, characterized in that Based on the second slurry, it includes 90-98 wt% of the second negative electrode active material, 0.5-5 wt% of the second conductive agent, and 0.5-5 wt% of the second binder; And / or, the second negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, silicon-based material, and tin-based material; and / or, the second conductive agent comprises at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, carbon nanotubes, graphene, metal powder or carbon fiber; And / or, the second binder includes at least one of styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polyvinyl alcohol, and polyvinylidene fluoride.

5. The preparation method according to claim 3 or 4, characterized in that The first slurry and the second slurry are the same; or, the first slurry and the second slurry are different.

6. A negative electrode plate, characterized in that: Obtained by the preparation method described in any one of claims 1 to 5, the negative electrode sheet includes a negative electrode current collector and a negative electrode layer located on one side in the height direction of the negative electrode current collector; the negative electrode layer includes a first negative electrode layer and a second negative electrode layer; in the width direction of the first negative electrode layer, the second negative electrode layer is located on both sides of the first negative electrode layer; the compaction density of the second negative electrode layer is ρ2, and the compaction density of the first negative electrode layer is ρ1; ρ2=ρ1×(1-k1); wherein k1 is 1%-5%.

7. The negative electrode sheet according to claim 6, characterized in that: In a height direction of the negative electrode current collector, the thickness of the second negative electrode layer is equal to the thickness of the first negative electrode layer.

8. A secondary battery, characterized in that: The secondary battery comprises the negative electrode sheet, a separator and a positive electrode sheet as described in claim 6 or 7; the positive electrode sheet, the separator and the negative electrode sheet are wound to form a battery cell.

9. An electrical device, characterized in that: The secondary battery according to claim 8 is included.

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