Lithium ion battery and relevant battery module, battery pack and apparatus

1. A lithium ion battery, comprising: a positive electrode plate, a negative electrode plate, a separator disposed between the positive electrode plate and the negative electrode plate, and an electrolytic solution, the positive electrode plate including a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector, and the electrolytic solution including an organic solvent, a lithium salt and an additive,

wherein the lithium salt comprises a primary lithium salt, the primary lithium salt is a first compound in an amount of 30% or more relative to the total molar amount of the lithium salt, and the first compound has a structure represented by the following formula I:

in which formula I, R 1 and R 2 each independently represent a fluorine atom, a fluoroalkyl group having 1-20 carbon atoms, or a fluoroalkoxy group having 1-20 carbon atoms, and wherein the additive comprises a second compound represented by the following formula II,

in which formula II, R 3 represents an alkylene group having 2-4 carbon atoms, a fluoroalkylene group having 2-4 carbon atoms, an alkyl-substituted alkylene group having 2-4 carbon atoms, an alkenylene group having 2-4 carbon atoms, a fluoroalkenylene group having 2-4 carbon atoms, an alkyl-substituted alkenylene group having 2-4 carbon atoms, an arylene group having 6-14 carbon atoms, and a fluorinated arylene group having 6-14 carbon atoms or an alkyl-substituted arylene group having 6-14 carbon atoms, and

wherein the positive electrode active material layer comprises a positive electrode active material represented by the structural formula Li a Ni 1-b M b O 2 , wherein a is in the range of 0.85 to 1.2, preferably 0.95 or more, b is in the range of 0 to 0.5, and M is at least one element selected from iron, cobalt, manganese, copper, zinc, aluminum, boron, gallium, and magnesium;

wherein a ratio M II /S of a mass M II (g) of the second compound to a total area S (m 2 ) of the positive electrode current collector is in the range of 0.1 g/m 2 to 3.1 g/m 2 ; and

wherein the lithium salt further comprises a secondary lithium salt and the secondary lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium bisoxalate borate and lithium perchlorate, preferably selected from one or two of lithium hexafluorophosphate and lithium tetrafluoroborate, and more preferably selected from lithium hexafluorophosphate; and

wherein a molar ratio of the primary lithium salt and the secondary lithium salt is in the range of 5:5 to 9:1, preferably in the range of 6:4 to 8:2.

2. The lithium ion battery according to claim 1 , wherein the first compound is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium fluorosulfonyl trifluoromethylsulfonyl imide, lithium bis(trifluoromethylsulfonyl)imide, lithium methylsulfonyl trifluoromethylsulfonyl imide, lithium trifluoromethylsulfonyl pentafluoroethylsulfonyl imide, lithium bis(pentafluoroethylsulfonyl) imide, LiN(SO 2 OCH 2 CF 3 ) 2 , LiN(SO 2 OCH 2 CF 2 CF 3 ) 2 , LiN(SO 2 OCH 2 CF 2 CF 2 H) 2 , LiN[(SO 2 OCH(CF 3 ) 2 ], preferably selected from one or two of lithium bis(fluorosulfonyl) imide and lithium methylsulfonyl trifluoromethanesulfonyl imide, and more preferably selected from lithium bis(fluorosulfonyl)imide.

3. The lithium ion battery according to claim 1 , wherein the second compound is selected from one or more of the following compounds:

4. The lithium ion battery according to claim 1 , wherein the second compound is present in an amount of 0.1 wt % to 3 wt % based on the total weight of the electrolytic solution.

5. The lithium ion battery according to claim 1 , wherein the organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, ethyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl propionate and tetrahydrofuran, preferably, the organic solvent is present in the electrolytic solution in a mass percentage of 65%-85%.

6. The lithium ion battery according to claim 1 , wherein a difference ΔV=V1−V2 between a corrosion potential V1 of the first compound to the positive current collector and a reduction potential V2 of the second compound satisfies 2.7V ≤ΔV≤4.2V.

7. The lithium ion battery according to claim 1 , wherein the battery has a charge cut-off voltage of 4.3V or higher, or has an energy density per unit mass of 250 wh/Kg.

8. A battery module comprising the lithium ion battery as claimed in claim 1 .

9. An apparatus comprising the lithium ion battery as claimed in claim 1 , wherein the lithium ion battery is used as a power source of the apparatus; preferably, the apparatus comprising electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric ships, or energy storage systems.