SECONDARY BATTERY, METHOD FOR PREPARING SECONDARY BATTERY, BATTERY MODULE, BATTERY PACK, AND ELECTRICAL APPARATUS

1 . A secondary battery comprising an electrolyte solution and a positive electrode plate, wherein,

the positive electrode plate comprises a layered material with a molecular formula of Li a Ni b Co c M1 d M2 e O f A g , wherein M1 is selected from one or both of Mn and Al, M2 is selected from one or more of Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te and W, and A is selected from one or more of F, N, P and S, with 0.8≤a≤1.2, 0<b<0.98, 0≤c<0.1, 0<d<0.5, 0≤e≤0.5, 0≤f≤2, 0≤g≤2, b+c+d+e=1, and f+g=2,

the electrolyte solution comprises lithium difluoro(oxalato)borate, and based on the total mass of the electrolyte solution, the percentage mass content of the lithium difluoro(oxalato)borate is x %, with 0<x≤1.0, and

the secondary battery satisfies c+x/10≥0.10.

2 . The secondary battery according to claim 1 , wherein the electrolyte solution further comprises one or more of fluoroethylene carbonate and lithium fluorosulfonylimide,

optionally, the molecular formula of the lithium fluorosulfonylimide is LiN(SO 2 R 1 )(SO 2 R 2 ), wherein R 1 and R 2 each independently represent F, or C n F 2n+1 , and n is an integer from 1 to 10; and

optionally, the lithium fluorosulfonylimide comprises one or both of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

3 . The secondary battery according to claim 2 , wherein,

based on the total mass of the electrolyte solution, the percentage mass content of the fluoroethylene carbonate is y %, with 0≤y≤2.5; and/or,

based on the total mass of the electrolyte solution, the percentage mass content of the lithium fluorosulfonylimide is z %, with 0≤z≤2.5.

4 . The secondary battery according to claim 3 , wherein the secondary battery further satisfies one or both of the following relational expressions (1)-(2):

0.5≤ y/x≤ 2.0, and  (1)

0.5≤ x/z≤ 2.0.  (2)

5 . The secondary battery according to claim 4 , wherein the secondary battery further simultaneously satisfies 0.5≤y/x≤2.0, 0.5≤x/z≤2.0 and 0.25≤y/z≤2.0.

6 . A method for preparing a secondary battery, at least comprising steps of:

step 1, assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte solution into a secondary battery,

the positive electrode plate comprises a layered material with a molecular formula of Li a Ni b Co c M1 d M2 e O f A g , wherein M1 is selected from one or both of Mn and Al, M2 is selected from one or more of Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te and W, and A is selected from one or more of F, N, P and S, with 0.8≤a≤1.2, 0<b<0.98, 0≤c<0.1, 0<d<0.5, 0≤e≤0.5, 0≤f≤2, 0≤g≤2, b+c+d+e=1, and f+g=2,

the electrolyte solution comprises lithium difluoro(oxalato)borate, optional fluoroethylene carbonate, and optional lithium fluorosulfonylimide,

based on the total mass of the electrolyte solution, the percentage mass content of the lithium difluoro(oxalato)borate is x %, with 0<x≤1.0, based on the total mass of the electrolyte solution, the percentage mass content of the fluoroethylene carbonate is y %, with 0≤y≤2.5, and based on the total mass of the electrolyte solution, the percentage mass content of the lithium fluorosulfonylimide is z %, with 0≤z≤2.5; and

step 2, selecting secondary batteries satisfying c+x/10≥0.10 from the secondary batteries obtained in step 1.

7 . The method according to claim 6 , further comprising a step of selecting secondary batteries satisfying 0.5≤y/x≤2.0 from the secondary batteries obtained in step 2.

8 . The method according to claim 6 , further comprising a step of selecting secondary batteries satisfying 0.5≤x/z≤2.0 from the secondary batteries obtained in step 2.

9 . The method according to claim 6 , further comprising a step of selecting secondary batteries simultaneously satisfying 0.5≤y/x≤2.0 and 0.5≤x/z≤2.0 from the secondary batteries obtained in step 2.

10 . The method according to claim 6 , further comprising a step of selecting secondary batteries simultaneously satisfying 0.5≤y/x≤2.0, 0.5≤x/z≤2.0 and 0.25≤y/z≤2.0 from the secondary batteries obtained in step 2.

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 apparatus, comprising the battery pack according to claim 12 .