Secondary battery, battery module, battery pack, and electrical device
A secondary battery, a battery module, a battery pack, and an electrical device are provided. The secondary battery includes a negative electrode plate, a positive electrode plate, and a separator located between the negative electrode plate and the positive electrode plate. The negative electrode plate or the separator includes a safety coating. A negative electrode charge capacity Nc and a positive electrode charge capacity Pc of the secondary battery satisfy: 0.45≤Nc/Pc<1, and/or, a negative electrode discharge capacity Nd and a positive electrode discharge capacity Pd of the secondary battery satisfy: 0.45≤Nd/Pd<1. By setting the values of Nc/Pc and/or Nd/Pd and disposing the safety coating in the secondary battery, this application achieves good cycle performance and safety performance while maintaining a high energy density of the secondary battery.
1 . A secondary battery, comprising a negative electrode plate, a positive electrode plate, and a separator located between the negative electrode plate and the positive electrode plate, wherein the negative electrode plate or the separator comprises a safety coating, the safety coating is disposed between the negative electrode plate and the separator and comprises an additive and a carbon material, the additive comprises a metal element, the safety coating allows deposition of lithium ion on a side of the safety coating adjacent to the negative electrode plate and allows formation of an alloy of the metal element and lithium in the safety coating during charge-and-discharge cycles of the secondary battery; and
a negative electrode charge capacity Nc and a positive electrode charge capacity Pc of the secondary battery satisfy: 0.6≤Nc/Pc<1, a negative electrode discharge capacity Nd and a positive electrode discharge capacity Pd of the secondary battery satisfy: 0.65≤Nd/Pd<1.
2 . The secondary battery according to claim 1 , wherein the negative electrode plate comprises a negative current collector and a negative film layer disposed on at least one surface of the negative current collector, and the safety coating is disposed on a surface of the negative film layer.
3 . The secondary battery according to claim 1 , wherein the safety coating is disposed on a first surface that is of the separator and that is oriented toward the negative electrode plate.
4 . The secondary battery according to claim 1 , wherein a thickness of the safety coating is 0.5 μm to 15 μm.
5 . The secondary battery according to claim 1 , wherein the negative electrode charge capacity Nc and the positive electrode charge capacity Pc of the secondary battery satisfy: 0.7≤Nc/Pc≤0.85.
6 . The secondary battery according to claim 1 , wherein the negative electrode discharge capacity Nd and the positive electrode discharge capacity Pd of the secondary battery satisfy: 0.65≤Nd/Pd≤0.87.
7 . The secondary battery according to claim 1 , wherein a negative film layer comprises a negative active material, and the negative active material comprises at least one of graphite, a silicon-carbon composite, silicon oxide, tin oxide, iron oxide, or titanium oxide.
8 . The secondary battery according to claim 1 , wherein the additive comprises the additive comprises at least one of a simple metal of gold, a simple metal of silver, a simple metal of magnesium, and a simple metal of aluminum, an oxide of silver, an oxide of magnesium, an oxide of aluminum, a nitrate of silver, a nitrate of magnesium, a nitrate of aluminum, a phosphate of silver, a phosphate of magnesium, a phosphate of aluminum, the carbon material comprises at least one of graphite, graphene, and carbon nanotube, a mass ratio between the additive and the carbon material is 0.05:100 to 100:100.
9 . The secondary battery according to claim 8 , wherein the mass ratio between the additive and the carbon material is 10:100 to 80:100.
10 . The secondary battery according to claim 8 , wherein the mass ratio between the additive and the carbon material is 20:100 to 50:100.
11 . A battery module, comprising the secondary battery according to claim 1 .
12 . A battery pack, comprising the battery module according to claim 11 .
13 . An electrical device, comprising the secondary battery according to claim 1 .
14 . An electrical device, comprising the secondary battery according to the battery module according to claim 11 .
15 . An electrical device, comprising the secondary battery according to the battery pack according to claim 12 .
16 . The secondary battery according to claim 8 , wherein the additive comprises at least one of a simple metal of silver and a simple metal of gold.
17 . The secondary battery according to claim 8 , wherein the additive comprises an oxide of silver.
18 . The secondary battery according to claim 8 , wherein the additive comprises at least one of a nitrate of silver and a phosphate of silver.
19 . The secondary battery according to claim 8 , wherein the additive comprises at least one of a nitrate of silver, a nitrate of magnesium, a phosphate of magnesium, and a phosphate of aluminum.
20 . The secondary battery according to claim 8 , wherein the safety coating is free from a silicon-containing compound.