Non-aqueous electrolytes and secondary batteries, battery modules, battery packs, and electrical devices containing them.

Abstract

To provide a nonaqueous electrolyte that simultaneously achieves a good cycle performance, a storage performance, and a dynamic performance of a secondary battery, the secondary battery containing the same, a battery module, a battery pack, and an electric device.SOLUTION: A nonaqueous electrolyte includes an electrolyte salt, and a nonaqueous solvent. The electrolyte salt includes a first lithium salt, a second lithium salt, and a third lithium salt. When calculated based on the total mass of the nonaqueous electrolyte, a content A1 of the first lithium salt, a content A2 of the second lithium salt, and a content A3 of the third lithium salt satisfy the following conditions: A1+A2+A3 is 1% or less, A1 / A2 is 0.016 to 40, and A1 / (A2+A3) is 0.006 to 13.5. The present application can simultaneously achieve a good cycle performance, a storage performance, and a dynamic performance of a secondary battery.SELECTED DRAWING: Figure 1

Claims

1. A secondary battery comprising an electrode assembly, a non-aqueous electrolyte, and an outer casing, The non-aqueous electrolyte comprises an electrolyte salt and a non-aqueous solvent. The electrolyte salt comprises a first lithium salt, a second lithium salt, and a third lithium salt. The first lithium salt has the structure represented by formula 1, R １ A represents a fluorine atom, or a partially or fully fluorinated C1-C10 alkyl group, and based on the total mass of the non-aqueous electrolyte, its mass content in the non-aqueous electrolyte is A1. The second lithium salt has the structure shown in formula 2, R ２ and R ３ Each of these independently represents a fluorine atom, or at least one selected from the group consisting of partially fluorinated or fully fluorinated C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C6-C8 aryl, C1-C10 alkoxy, C2-C10 alkenyloxy, C2-C10 alkynyloxy, and C6-C8 aryloxy, and calculated based on the total mass of the non-aqueous electrolyte, its mass content in the non-aqueous electrolyte is A2. The third lithium salt is selected from lithium tetrafluoroborate, and its mass content in the non-aqueous electrolyte is calculated to be A3 based on the total mass of the non-aqueous electrolyte. The aforementioned non-aqueous electrolyte is (1) A1 is 0.005% to 0.2%, (2) A2 is 0.005% to 0.3%, (3) A3 is a secondary battery that satisfies the requirement of 0.01% to 0.5%. 【Chemistry 1】 【Chemistry 2】

2. A1 / A2 is 0.03 to 10 and / or A1 / (A2+A3) is between 0.02 and 3.

5. The secondary battery according to claim 1.

3. The non-aqueous electrolyte further satisfies the condition that A3 / A2 is 0.04 to 30. The secondary battery according to claim 1.

4. The secondary battery according to any one of claims 1 to 3, wherein the non-aqueous electrolyte satisfies the following conditions: A1 + A2 + A3 is 1% or less, A1 / A2 is 0.016 to 40, and A1 / (A2 + A3) is 0.006 to 13.

5.

5. The first lithium salt comprises at least one of the following compounds: 【Transformation 3】 and / or, The secondary battery according to any one of claims 1 to 3, wherein the second lithium salt comprises at least one of the following compounds. 【Chemistry 4】

6. The electrolyte salt further comprises at least one of the fourth lithium salt and the fifth lithium salt, The fourth lithium salt is lithium hexafluorophosphate, and based on the total mass of the non-aqueous electrolyte, its mass content in the non-aqueous electrolyte is A4. The fifth lithium salt is lithium bisfluorosulfonylimide, and based on the total mass of the non-aqueous electrolyte, its mass content in the non-aqueous electrolyte is A5. The non-aqueous electrolyte satisfies the condition that A4 + A5 is 10% to 20%. A secondary battery according to any one of claims 1 to 3.

7. (A4 + A5) / (A1 + A2 + A3) is between 10 and 200. The secondary battery according to claim 6.

8. The non-aqueous solvent comprises a first solvent, a second solvent, and a third solvent. The first solvent comprises at least one of ethylene carbonate, propylene carbonate, and butylene carbonate, and its mass content in the non-aqueous solvent is calculated to be B1 based on the total mass of the non-aqueous solvent. The second solvent comprises at least one of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate, and its mass content in the nonaqueous solvent is calculated to be B2 based on the total mass of the nonaqueous solvent. The third solvent comprises at least one of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate, and calculated based on the total mass of the nonaqueous solvent, its mass content in the nonaqueous solvent is B3. The non-aqueous electrolyte satisfies the following conditions: B1 is 10% to 30%, B2 is 50% to 90%, and B3 is 0% to 20%. A secondary battery according to any one of claims 1 to 3.

9. The non-aqueous electrolyte further comprises a first additive, the first additive comprising at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, and 1,3-propanesultone, and the mass content of the first additive in the non-aqueous electrolyte, calculated based on the total mass of the non-aqueous electrolyte, is C1, and C1 is 0.05% to 2%. A secondary battery according to any one of claims 1 to 3.

10. The non-aqueous electrolyte further satisfies the condition that (C1 + A5) / B1 is 0.3 to 0.

8. The secondary battery according to claim 9.

11. The non-aqueous electrolyte further comprises a second additive, the second additive comprising at least one of sulfamic acid and its salts, and the mass content of the second additive in the non-aqueous electrolyte, calculated based on the total mass of the non-aqueous electrolyte, is C2, and the amount of C2 is 0.005% to 0.1%. A secondary battery according to any one of claims 1 to 3.

12. The electrode assembly includes a positive electrode sheet and a negative electrode sheet, the charge transfer resistance of the positive electrode sheet is Rct1, and the charge transfer resistance of the negative electrode sheet is Rct2, where Rct1 / Rct2 is 0.5 to 2. The charge transfer resistance of the positive electrode sheet is obtained by a test method in which the positive electrode sheet is assembled into a symmetrical battery, its electrochemical impedance spectrum is measured using the electrochemical AC impedance method of an electrochemical workstation, a Nyquist plot is created, the Nyquist plot obtained using the equivalent circuit curve approximation method is analyzed, and the semicircular diameter is defined as the charge transfer resistance Rct1 of the positive electrode sheet. The charge transfer resistance of the negative electrode sheet is obtained by a test method in which the negative electrode sheet is assembled into a symmetrical battery, its electrochemical impedance spectrum is measured using the electrochemical AC impedance method of an electrochemical workstation, a Nyquist diagram is created, the Nyquist diagram obtained using the equivalent circuit curve approximation method is analyzed, and the semicircular diameter is defined as the charge transfer resistance Rct2 of the negative electrode sheet. The secondary battery according to claim 1.

13. The non-aqueous electrolyte includes a first electrolyte that permeates the electrode assembly, and a second electrolyte located between the electrode assembly and the outer casing. Based on the total mass of the first electrolyte, the sum of the mass contents of the first lithium salt, the second lithium salt, the third lithium salt, the first additive, and the second additive in the first electrolyte is X1. Based on the total mass of the second electrolyte, the sum of the mass contents of the first lithium salt, the second lithium salt, the third lithium salt, the first additive, and the second additive in the second electrolyte is X2. 0.5 ≤ X1 / X2 < 1, The first electrolyte is obtained by a test method in which, after discharging the secondary battery to the discharge termination voltage, the electrode assembly is disassembled and subjected to centrifugation, and the liquid obtained by subsequent centrifugation is the first electrolyte. The secondary battery according to claim 1.

14. The positive electrode sheet contains a layered material with the molecular formula Li ａ Ni ｂ Co ｃ Mn ｄ Al ｅ M ｆ O ｇ A ｈ where M represents a doping cation of the transition metal site, A represents a doping anion of the oxygen site, 0.8 ≤ a ≤ 1.2, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, 0 ≤ e ≤ 1, 0 ≤ f ≤ 0.2, 0 ≤ g ≤ 2, 0 ≤ h ≤ 2, b + c + d + e + f = 1, and g + h = 2. The secondary battery according to claim 1.

15. Li ａ Ni ｂ Co ｃ Mn ｄ Al ｅ M ｆ O ｇ A ｈ は、 (1) M is selected from at least one of Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W. (2) A is selected from at least one of F, N, P and S. (3) 0 < b < 0.98, (4) c = 0, (5) 0 < c ≤ 0.20, (6) d = 0 and 0 < e < 0.50, (7) e = 0 and 0 < d < 0.50, (8) 0 < d < 0.50 and 0 < e < 0.50, A secondary battery according to claim 14, satisfying at least one of the above conditions (1) to (8).

16. A battery module comprising the secondary battery described in claim 1.

17. A battery pack comprising a secondary battery according to claim 1 and a battery module according to claim 16.

18. An electrical device comprising at least one of the secondary battery described in claim 1, the battery module described in claim 16, and the battery pack described in claim 17.

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