SECONDARY BATTERY, AND BATTERY MODULE, BATTERY PACK, AND ELECTRIC APPARATUS CONTAINING SAME

1 . A secondary battery, comprising an electrolyte and a negative electrode, wherein

the electrolyte comprises a low-viscosity solvent, an electrolyte salt, and a high-dielectric-constant solvent, wherein

a viscosity of the low-viscosity solvent at 25° C. is 0.3 mPa·s-0.6 mPa·s;

a dielectric constant of the high-dielectric-constant solvent is 30 F/m-100 F/m, and a percentage of the high-dielectric-constant solvent in total solvent in the electrolyte by mass is higher than 20%; and

the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector; and

the secondary battery satisfies the following relational expression:

1

×

1

⁢

0

-

4

≤

B

×

C

×

P

OI

×

CW

≤

1

×

1

⁢

0

-

3

,

wherein B is a percentage of the low-viscosity solvent in total solvent in the electrolyte by mass; C is a percentage of the electrolyte salt in the electrolyte by mass; P is a porosity of the negative electrode active material layer; CW is a coating weight of the negative electrode active material layer, measured in mg/cm 2 ; and OI is an orientation index of the negative electrode active material layer; and

OI=C004/C110, C004 is a peak area of a 004 characteristic diffraction peak in an X-ray diffraction pattern of the negative electrode active material layer, and C110 is a peak area of a 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer.

2 . The secondary battery according to claim 1 , wherein the low-viscosity solvent comprises at least one selected from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA), and acetonitrile (ACN).

3 . The secondary battery according to claim 1 , wherein the percentage B of the low-viscosity solvent in total solvent in the electrolyte by mass is 10%-80%, and optionally, 20%-70%.

4 . The secondary battery according to claim 1 , wherein the percentage C of the electrolyte salt in the electrolyte by mass is 10%-23%, and optionally, 13%-20%.

5 . The secondary battery according to claim 1 , wherein the high-dielectric-constant solvent comprises cyclic carbonate, optionally, the cyclic carbonate comprises at least one selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and fluoroethylene carbonate.

6 . The secondary battery according to claim 1 , wherein the percentage C of the high-dielectric-constant solvent in the total solvent in the electrolyte by mass is 20%-40%.

7 . The secondary battery according to claim 1 , wherein the electrolyte further comprises at least one selected from diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate, and ethyl propionate.

8 . The secondary battery according to claim 1 , wherein the electrolyte further comprises a film-forming additive, and

the film-forming additive comprises at least one selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3-propane sultone, lithium difluorophosphate, lithium bisfluorooxalate borate, nitrile compound, and cyclic sulfate, and optionally, the cyclic sulfate is ethylene sulfate.

9 . The secondary battery according to claim 1 , wherein a conductivity of the electrolyte at 25° C. is 8 mS/cm-16 mS/cm.

10 . The secondary battery according to claim 1 , wherein a viscosity of the electrolyte at 25° C. is 1 mPa·s-7 mPa·s.

11 . The secondary battery according to claim 1 , wherein an OI value of the negative electrode active material layer is 3-24.

12 . The secondary battery according to claim 1 , wherein a coating weight CW of the negative electrode active material layer is 6.5 mg/cm 2 -19.5 mg/cm 2 .

13 . The secondary battery according to claim 1 , wherein a porosity P of the negative electrode active material layer is 20%-60%.

14 . The secondary battery according to claim 1 , wherein the electrolyte salt comprises at least one selected from NaPF 6 , NaClO 4 , NaBCl 4 , NaSO 3 CF 3 , and Na(CH 3 )C6H 4 SO 3 .

15 . The secondary battery according to claim 1 , wherein the negative electrode active material comprises at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon, and a silicon-based material, and optionally, the silicon-based material comprises at least one selected from elemental silicon, silicon oxide, silicon carbon composite, and silicon-based alloy.

16 . The secondary battery according to claim 14 , wherein the negative electrode active material comprises at least one selected from natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, trioxide molybdenum, elemental phosphorus, sodium titanate, and sodium terephthalate.

17 . The secondary battery according to claim 15 , wherein a percentage of the silicon-based material in a total negative electrode active material by mass is 0%-30%, and optionally, 0%-10%.

18 . The secondary battery according to claim 1 , wherein the secondary battery further comprises a positive electrode, and

the positive electrode comprises a positive electrode active material with a molecular formula of LiNi x Co y Mn z M 1-x-y-z O 2 , wherein 0≤x≤1, 0≤y≤0.5, 0≤z≤0.5, and x+y+z=1, optionally, 0.5≤x≤0.9, 0≤y≤0.3, and 0≤z≤0.3, and M is at least one selected from Zr, Al, Mg, Sb, Fe, Cu, and W.

19 . The secondary battery according to claim 1 , wherein the secondary battery further comprises a positive electrode, and

the positive electrode comprises at least one selected from the following positive electrode active materials: layered transition metal oxide, polyanionic compound, Prussian blue compound, sulfide, nitride, carbide, and titanate.

20 . An electric apparatus, comprising the secondary battery according to claim 1 .