Lithium-ion secondary battery, battery module, battery pack, and powered device

1. A lithium-ion secondary battery, comprising a bare battery cell accommodating cavity in which a bare battery cell group comprising one or more bare cells A and one or more bare cells B is arranged, wherein the bare cell A comprises a first positive electrode sheet comprising a first positive-electrode active material selected from a single crystal or single crystal-like low-nickel ternary positive electrode material A1, wherein single crystal-like ternary low-nickel electrode material comprises primary particles and secondary particles and volume distribution of secondary particles formed by agglomeration is 10% to 35%, the bare cell B comprises a second positive electrode sheet comprising a second positive-electrode active material and/or a third positive-electrode active material, the second positive-electrode active material is selected from a polycrystalline high-nickel ternary positive electrode material B1, and the third positive-electrode active material is selected from a polycrystalline low-nickel ternary positive electrode material B2; wherein mole fraction of low-nickel is greater than 0 and less than or equal to 0.65 and mole fraction of high nickel is greater than or equal to 0.7 and less than 1, wherein 100% SOC charged unit cell volume shrinkage rate of the single crystal or single crystal-like low-nickel ternary positive electrode material A1 is ≤3%;

and/or, the 100% SOC charged unit cell volume shrinkage rate of the polycrystalline high-nickel ternary positive electrode material B1 is ≥4%;

and/or, the 100% SOC charged unit cell volume shrinkage rate of the polycrystalline low-nickel ternary positive electrode material B2 is ≤3%.

2. The lithium-ion secondary battery according to claim 1 , wherein the molecular formula of the single crystal or single crystal-like low-nickel ternary positive electrode material A1 is LiNi x1 Co y1 Mn 1-x1-y1 O 2 , wherein 0<x1≤0.65, 0<y1<0.35, 0<1−x1−y1<0.35.

3. The lithium-ion secondary battery according to claim 1 , wherein the molecular formula of the single crystal or single crystal-like low-nickel ternary positive electrode material A1 is LiNi x1 Co y1 Mn 1-x1-y1 O 2 , wherein 0<x1≤0.55, 0<y1<0.45, 0<1−x1−y1<0.45.

4. The lithium-ion secondary battery according to claim 1 , wherein the molecular formula of the polycrystalline high-nickel ternary positive electrode material B1 is LiNi x2 Co y2 Mn 1-x2-y2 O 2 , wherein 0.7≤x2<1, 0<y2<0.3, 0<1−x2−y2<0.3.

5. The lithium-ion secondary battery according to claim 1 , wherein the molecular formula of the polycrystalline low-nickel ternary positive electrode material B2 is LiNi x3 Co y3 Mn 1-x3-y3 O 2 , wherein 0<x3≤0.65, 0<y3<0.35, 0<1−x3−y3<0.35.

6. The lithium-ion secondary battery according to claim 1 , wherein the molecular formula of the polycrystalline low-nickel ternary positive electrode material B2 is LiNi x3 Co y3 Mn 1-x3-y3 O 2 , wherein 0<x3≤0.55, 0<y3<0.45, 0<1−x3−y3<0.45.

7. The lithium-ion secondary battery according to claim 1 , wherein the bare cell B is distributed closer to the outside of the bare cell group than the bare cell A.

8. The lithium-ion secondary battery according to claim 1 , wherein the bare cell A is distributed closer to the middle of the bare cell group than the bare cell B.

9. The lithium-ion secondary battery according to claim 1 , wherein the second positive electrode sheet further comprises a fourth positive-electrode active material selected from a single crystal or single crystal-like low-nickel ternary positive electrode material A2, and the molecular formula of the single crystal or single crystal-like low-nickel ternary positive electrode material A2 is LiNi x4 Co y4 Mn 1-x4-y4 O 2 , wherein 0<x4≤0.65, 0<y4<0.35, 0<1−x4−y4<0.35.

10. The lithium-ion secondary battery according to claim 9 , wherein 100% SOC charged unit cell volume shrinkage rate of the single crystal or single crystal-like low-nickel ternary positive electrode material A2 is ≤3%.

11. The lithium-ion secondary battery according to claim 1 , wherein the second positive electrode sheet further comprises a fourth positive-electrode active material selected from a single crystal or single crystal-like low-nickel ternary positive electrode material A2, and the molecular formula of the single crystal or single crystal-like low-nickel ternary positive electrode material A2 is LiNi x4 Co y4 Mn 1-x4-y4 O 2 , wherein 0<x4≤0.55, 0<y4<0.45, 0<1−x4−y4<0.45.

12. The lithium-ion secondary battery according to claim 1 , wherein in the lithium-ion secondary battery, a mass ratio k of the total mass of the single crystal positive-electrode active material to the total mass of the polycrystalline positive-electrode active material is 0.5-9.

13. The lithium-ion secondary battery according to claim 1 , wherein a coating amount of a negative electrode in the bare cell A is ≤0.150 g/1540.25 mm{circumflex over ( )}2.

14. A battery module comprising the lithium-ion secondary battery according to claim 1 .

15. A battery pack comprising the battery module according to claim 14 .

16. A powered device comprising the battery pack according to claim 15 .

17. A powered device comprising the battery module according to claim 14 .

18. A powered device comprising one or more selected from the lithium-ion secondary battery according to claim 1 .