Negative electrode active material and preparation method thereof, as well as secondary battery having the same
Provided are a negative electrode active material and a preparation method thereof, as well as a secondary battery having the same, and a battery module, a battery pack and an electrical apparatus. The negative electrode active material of the present application comprises: a silicon inner core; a first cladding layer clad on the surface of the silicon inner core, wherein the first cladding layer is a carbon-containing layer; and a second cladding layer clad on the surface of the first cladding layer, wherein the second cladding layer is an elemental sulfur layer. By using the negative electrode active material of the present application, the energy density of the secondary battery can be improved, and the cycle life can be prolonged.
1 . A negative electrode active material, comprising:
a silicon inner core comprising silicon monoxide;
a first cladding layer clad on a surface of the silicon inner core, wherein the first cladding layer comprises carbon resulting from heating a carbon source material comprising glucose; and
a second cladding layer clad on a surface of the first cladding layer, wherein the second cladding layer is an elemental sulfur layer comprising elemental sulfur,
wherein the second cladding layer has a coverage ratio of 70% to 100%,
a sulfur content of the elemental sulfur in the second cladding layer is 0.5 mass % to 3 mass %, based on a total mass of the negative electrode active material,
a carbon content of the carbon in the first cladding layer is 1.1 mass % to 4.9 mass %, based on a total mass of the negative electrode active material,
the second cladding layer has a thickness of 10 nm to 47 nm, the first cladding layer has a thickness of 12 nm to 98 nm, and the negative electrode active material has a particle size of 1 μm to 7 μm.
2 . The negative electrode active material according to claim 1 , wherein,
the sulfur content is 1.2 mass % to 3 mass % based on a total mass of the negative electrode active material.
3 . The negative electrode active material according to claim 1 , wherein,
the carbon content in the first cladding layer is 2.3 mass % to 4.9 mass % based on a total mass of the negative electrode active material.
4 . The negative electrode active material according to claim 1 , wherein,
a mass ratio of the carbon content to the sulfur content is 0.33 to 23 in the negative electrode active material.
5 . The negative electrode active material according to claim 1 , wherein,
a mass ratio of the elemental sulfur to the silicon inner core is 0.10% to 4.27% in the negative electrode active material.
6 . The negative electrode active material according to claim 1 , wherein,
a mass ratio of the silicon inner core to the carbon is 15.47 to 246 in the negative electrode active material.
7 . The negative electrode active material according to claim 1 , wherein,
the silicon inner core further comprises silicon alloy, the silicon alloy is one or more selected from ferrosilicon alloy, silicon-aluminum alloy, silicomanganese alloy, silicon-tin alloy, and silicon-germanium alloy.
8 . The negative electrode active material according to claim 1 , wherein,
the second cladding layer has a thickness of 4 nm to 70 nm, the first cladding layer has a thickness of 5 nm to 120 nm, and the negative electrode active material has a particle size of 0.5 μm to 8 μm.
9 . A secondary battery comprising the negative electrode active material of claim 1 and an electrolyte solution, wherein the electrolyte solution comprises fluoroethylene carbonate, a content of the fluoroethylene carbonate is 2 mass % to 10 mass %.
10 . The secondary battery according to claim 9 , wherein,
the electrolyte solution further comprises vinylene carbonate, a content of the vinylene carbonate is 0.5 mass % to 2 mass %.
11 . The secondary battery according to claim 9 , wherein,
a mass ratio of a content of fluoroethylene carbonate in the electrolyte solution to a sulfur content in the negative electrode active material is 0.42 to 60.
12 . The secondary battery according to claim 10 , wherein,
a ratio of the content of the fluoroethylene carbonate to the content of the vinylene carbonate is 0.3 to 5.5 in the electrolyte solution.
13 . A battery module comprising the secondary battery according to claim 9 .
14 . A battery pack comprising the battery module according to claim 13 .
15 . An electrical apparatus comprising the secondary battery according to claim 9 .