NEGATIVE ELECTRODE PLATE, PREPARATION METHOD THEREFOR, SECONDARY BATTERY INCLUDING SAME, AND POWER CONSUMING DEVICE
A negative electrode plate includes a negative current collector and a negative film layer located on a surface of the negative current collector. The negative film layer has a length direction consistent with a length direction of the negative current collector and a width direction consistent with a width direction of the negative current collector. A cross section of the negative film layer perpendicular to the length direction includes a uniform thickness region located at a middle portion in the width direction and edge regions located at two ends in the width direction. Either of the edge regions has a thickness continuously decreasing in a direction from the uniform thickness region to the edge region. A width a of either of the two edge regions and an average thickness d of the uniform thickness region satisfy a/d≤1.5 and d≤300 μm.
1 . A negative electrode plate, comprising:
a negative current collector; and
a negative film layer located on a surface of the negative current collector;
wherein:
the negative film layer has a length direction consistent with a length direction of the negative current collector and a width direction consistent with a width direction of the negative current collector;
a cross section of the negative film layer perpendicular to the length direction comprises a uniform thickness region located at a middle portion in the width direction of the negative film layer and edge regions located at two ends in the width direction the negative film layer;
either of the edge regions has a thickness continuously decreasing in a direction from the uniform thickness region to the edge region, and
a width a of either of the edge regions and an average thickness d of the uniform thickness region satisfy:
a/d≤ 1.5, and
d≤ 300 μm.
2 . The negative electrode plate of claim 1 , wherein a/d≤1.
3 . The negative electrode plate of claim 1 , wherein the negative film layer comprises a negative active material, a conductive agent, a first binder, and a second binder;
the first binder comprises at least one of (methyl) acrylic acid, polyacrylamide, cellulose ether or salt thereof, or starch ether or salt thereof; and
the second binder comprises at least one of acrylate-ethylene, styrene butadiene rubber, nitrile rubber, acrylate, or polyurethane.
4 . The negative electrode plate of claim 3 , wherein the first binder comprises sodium carboxymethyl cellulose, the sodium carboxymethyl cellulose having a weight-average molecular weight of 400000 or less.
5 . The negative electrode plate of claim 3 , wherein the first binder comprises sodium carboxymethyl cellulose, the sodium carboxymethyl cellulose having a degree of substitution in a range of 0.65-0.8.
6 . The negative electrode plate of claim 3 , wherein the first binder comprises sodium carboxymethyl starch, the sodium carboxymethyl starch having a polydispersity index (PDI) in a range of 2.0-5.5.
7 . The negative electrode plate of claim 3 , wherein the first binder comprises sodium carboxymethyl starch, the sodium carboxymethyl starch having a weight-average molecular weight of 400000 or more.
8 . The negative electrode plate of claim 3 , wherein the second binder is styrene butadiene rubber having a volume average particle size Dv50 satisfying: 80 nm≤Dv50≤200 nm.
9 . The negative electrode plate of claim 3 , wherein the first binder and the second binder have a mass content ratio ranging from 2:1 to 1:2.
10 . A method for preparing a negative electrode plate, comprising:
coating a negative current collector with a negative slurry; and
obtaining the negative electrode plate by means of drying and cold pressing of the negative slurry, the negative electrode plate comprising:
the negative current collector; and
a negative film layer located on a surface of the negative current collector;
wherein:
the negative film layer has a length direction consistent with a length direction of the negative current collector and a width direction consistent with a width direction of the negative current collector;
a cross section of the negative film layer perpendicular to the length direction comprises a uniform thickness region located at a middle portion in the width direction of the negative film layer and edge regions located at two ends in the width direction the negative film layer;
either of the edge regions has a thickness continuously decreasing in a direction from the uniform thickness region to the edge region, and
a width a of either of the edge regions and an average thickness d of the uniform thickness region satisfy:
a/d≤ 1.5, and
d≤ 300 μm.
11 . The method of claim 10 , wherein the negative slurry has a solid component content of greater than or equal to 60% by mass.
12 . The method of claim 10 ,
wherein the negative slurry comprises a negative active material, a conductive agent, a first binder, and a second binder;
the method further comprising:
mixing the negative active material, the conductive agent, the first binder, the second binder, and deionized water to obtain the negative slurry;
wherein:
coating the negative current collector with the negative slurry comprises coating the negative slurry on the surface of the negative current collector by extrusion;
the first binder is at least one of (methyl) acrylic acid, polyacrylamide, cellulose ether or salt thereof, or starch ether or salt thereof; and
the second binder is at least one of acrylate-ethylene, styrene butadiene rubber, nitrile rubber, acrylate, or polyurethane.
13 . The method of claim 12 , wherein the first binder comprises sodium carboxymethyl cellulose, the sodium carboxymethyl cellulose having a weight-average molecular weight of 400000 or less.
14 . The method of claim 12 , wherein the first binder comprises sodium carboxymethyl cellulose, the sodium carboxymethyl cellulose having a degree of substitution in a range of 0.65-0.8.
15 . The method of claim 12 , wherein the first binder comprises sodium carboxymethyl starch, the sodium carboxymethyl starch having a polydispersity index (PDI) in a range of 2.0-5.5.
16 . The method of claim 12 , wherein the first binder comprises sodium carboxymethyl starch, the sodium carboxymethyl starch having a weight-average molecular weight of 400000 or more.
17 . The method of claim 12 , wherein the second binder is styrene butadiene rubber having a volume average particle size Dv50 satisfying: 80 nm≤Dv50≤200 nm.
18 . The method of claim 12 , wherein the first binder and the second binder have a mass content ratio ranging from 2:1 to 1:2.
19 . A secondary battery, comprising:
a negative electrode plate comprising:
a negative current collector; and
a negative film layer located on a surface of the negative current collector;
wherein:
the negative film layer has a length direction consistent with a length direction of the negative current collector and a width direction consistent with a width direction of the negative current collector;
a cross section of the negative film layer perpendicular to the length direction comprises a uniform thickness region located at a middle portion in the width direction of the negative film layer and edge regions located at two ends in the width direction the negative film layer;
either of the edge regions has a thickness continuously decreasing in a direction from the uniform thickness region to the edge region, and
a width a of either of the edge regions and an average thickness d of the uniform thickness region satisfy:
a/d≤ 1.5, and
d≤ 300 μm.
20 . A power consuming device, comprising the secondary battery of claim 19 .