Secondary battery and device including the same
The application provides a secondary battery and a device including the same. The second battery includes: a negative electrode plate, the negative electrode plate including a negative active material; a separation film, the separation film including a base material and a coating arranged on at least one surface of the base material; and an electrolyte, the electrolyte including an organic solvent, where the negative active material includes a silicon-based material and a carbon material; thickness of the base material of the separation film is 7 μm˜12 μm; and the organic solvent includes ethylene carbonate, and a weight ratio of the ethylene carbonate in the organic solvent is ≤20%. The secondary battery and the device including the same, which are provided by the application, in the premise of having high energy density, can also have good high-temperature cycle performance, good high-temperature storage performance, and low low-temperature direct current resistance.
1. A secondary battery, comprising:
a negative electrode plate, including a negative current collector and a negative electrode film which is arranged on at least one surface of the negative current collector and includes a negative active material;
a separation film, including a base material and a coating arranged on at least one surface of the base material; and
an electrolyte, including an organic solvent,
wherein the negative active material includes a silicon-based material and a carbon material;
a thickness of the base material of the separation film is 7 μm˜12 μm; and
the organic solvent includes ethylene carbonate (EC) and a weight ratio of the ethylene carbonate (EC) in the organic solvent is ≤20%,
wherein the electrolyte further includes electrolyte salt, and the electrolyte salt includes lithium bisfluorosulfonimide (LiFSI) and lithium hexafluorophosphate (LiPF 6 ); and
molarity of the lithium bisfluorosulfonimide (LiFSI) in the electrolyte is 0.8 mol/L˜1.3 mol/L, and molarity of the lithium hexafluorophosphate (LiPF 6 ) in the electrolyte is 0.15 mol/L˜0.4 mol/L.
2. The secondary battery according to claim 1 , wherein the weight ratio of the ethylene carbonate (EC) in the organic solvent is ≤15%.
3. The secondary battery according to claim 1 , wherein the thickness of the base material of the separation film is 7 μm˜10 μm.
4. The secondary battery according to claim 1 , wherein a porosity of the separation film is 25%˜50%.
5. The secondary battery according to claim 1 , wherein the organic solvent further includes one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC).
6. The secondary battery according to claim 5 , wherein a weight ratio of the ethyl methyl carbonate (EMC) in the organic solvent is 60%˜95%.
7. The secondary battery according to claim 5 , wherein a weight ratio of the diethyl carbonate (DEC) in the organic solvent is ≤30%.
8. The secondary battery according to claim 5 , wherein a weight ratio of the dimethyl carbonate (DMC) in the organic solvent is ≤15%.
9. The secondary battery according to claim 8 , wherein the molarity of the lithium bisfluorosulfonimide (LiFSI) in the electrolyte is 0.9 mol/L˜1.2 mol/L, and the molarity of the lithium hexafluorophosphate (LiPF 6 ) in the electrolyte is 0.15 mol/L˜0.3 mol/L.
10. The secondary battery according to claim 1 , wherein
electrical conductivity of the electrolyte at 25° C. is 6.5 mS/cm˜9.5 mS/cm; and
a viscosity of the electrolyte at 25° C. is 3.5 mPa·s˜5.5 mPa·s.
11. The secondary battery according to claim 1 , wherein a mass ratio of the silicon-based material in the negative active material is 15%˜30%.
12. The secondary battery according to claim 1 , wherein a thickness of the separation film is 12 μm˜14 μm.
13. The secondary battery according to claim 1 , further comprising a positive electrode plate, the positive electrode plate including a positive current collector and a positive electrode film which is arranged on at least one surface of the positive current collector and includes a positive active material, the positive active material including one or more of a lithium nickel cobalt manganese oxygen compound and a lithium nickel cobalt aluminum oxide.
14. A device, comprising the secondary battery according to claim 1 .