Wound electrode assembly, lithium-ion secondary battery and negative electrode plate

1. A wound electrode assembly for lithium-ion secondary battery, wherein the wound electrode assembly comprises a negative electrode plate comprising a negative electrode current collector and negative active material layers disposed on two opposite surfaces of the negative electrode current collector, and the negative active material layer comprises a negative active material; and

wherein the two negative active material layers respectively comprise an active material layer in an unpaired region facing no positive electrode plate and an active material layer in a paired region distributed successively in the length direction of the negative electrode plate, wherein the paired region has an opposite positive electrode plate, and two active material layers in the unpaired regions are arranged at both ends in the length direction of the negative electrode plate, and a first metallic lithium layer is disposed on the surface of one or both of the two active material layers in the unpaired regions, so that to form a first lithium pre-intercalation compound in either or both of the active material layers in the two unpaired regions; and

characterized in that, in each of the negative active material layers, the ratio of the area of the active material layer in the paired region to the area of the active material layer in the unpaired region is from 99:1 to 4:1.

2. The wound electrode assembly according to claim 1 , wherein the first metallic lithium layer is disposed on a surface of the active material layer in the unpaired region that faces away from the negative electrode current collector.

3. The wound electrode assembly according to claim 1 , wherein a ratio of a weight of the first metallic lithium layer per unit area to a weight of the active material layer in the unpaired region per unit area is from 0.5% to 10%.

4. The wound electrode assembly according to claim 1 , wherein a second metallic lithium layer is further disposed on the surface of one or both of the active material layers in the paired region, so as to form a second lithium pre-intercalation compound in either or both of the two paired active material layer regions.

5. The wound electrode assembly according to claim 4 , wherein a ratio of a weight of the second metallic lithium layer per unit area to a weight of the active material layer in the paired regions per unit area is from 0.5% to 10%.

6. The wound electrode assembly according to claim 1 , wherein the negative active material is one or more of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, nano-carbon, carbon fiber, elemental silicon, silicon-oxygen compound, silicon-carbon composite, silicon alloy, elemental tin, tin-oxygen compound, tin-carbon composite, tin alloy and lithium titanate.

7. The wound electrode assembly according to claim 1 , wherein the negative active material comprises a carbon-based negative active material.

8. The wound electrode assembly according to claim 1 , wherein the negative active material comprises one or more of natural graphite and artificial graphite.

9. A lithium ion secondary battery comprising a wound electrode assembly according to claim 1 .

10. The lithium ion secondary battery according to claim 9 , wherein the active material layer in the unpaired region comprises a first lithium pre-intercalation compound, and a ratio of a active lithium content of the active material layer in the unpaired region to a gram capacity of the negative active material in the active material layer in the unpaired region is from 0.005 to 0.95.

11. A negative electrode plate for lithium-ion secondary battery, characterized in that, the negative electrode plate is as defined in claim 1 .