Porous anode active material, method of preparing the same, and anode and lithium battery employing the same
Provided are a porous anode active material, a method of preparing the same, and an anode and a lithium battery employing the same. The porous anode active material includes fine particles of metallic substance capable of forming a lithium alloy; a crystalline carboneous substance; and a porous carboneous material coating and attaching to the fine particles of metallic substance and the crystalline carboneous substance, the porous anode active material having pores exhibiting a bimodal size distribution with two pore diameter peaks as measured by a Barrett-Joyner-Halenda (BJH) pore size distribution from a nitrogen adsorption. The porous anode active material has the pores having a bimodal size distribution, and thus may efficiently remove a stress occurring due to a difference of expansion between a carboneous material and a metallic active material during charging and discharging. Further, the anode electrode and the lithium battery comprising the anode active material have excellent charge/discharge characteristics.
1. A porous anode active material comprising:
fine particles of metallic substance capable of forming a lithium alloy;
a crystalline carboneous substance; and
a porous carboneous material coating and binding the fine particles of metallic substance and the crystalline carboneous substance,
the porous anode active material having pores exhibiting a bimodal size distribution with two pore diameter peaks in a Barrett-Joyner-Halenda (BJH) pore size distribution as measured by a nitrogen adsorption test.
2. A porous anode active material comprising:
fine particles of metallic substance capable of forming a lithium alloy,
a crystalline carboneous substance; and
a porous carboneous material coating and binding the fine particles of metallic substance and the crystalline carboneous substance,
the porous anode active material having pores exhibiting a bimodal size distribution with two pore diameter peaks in a Barrett-Joyner-Halenda (BJH) pore size distribution as measured by a nitrogen adsorption test, wherein the pores have a first peak in a range of the pore size from 1 nm to less than 10 nm and a second peak in a range of the pore size from greater than 10 nm to 100 nm.
3. The porous anode active material of claim 2 , wherein the pores have a first peak in a range of the pore size of 2-8 nm and a second peak in a range of the pore size of 20-80 nm.
4. The porous anode active material of claim 1 , having a pore volume of 0.2-2 cm 3 /g.
5. The porous anode active material of claim 1 , having a porosity of 5-60%.
6. The porous anode active material of claim 1 , wherein average pore diameters corresponding to the two pore diameter peaks are respectively 2-8 nm and 20-80 nm.
7. The porous anode active material of claim 1 , wherein the metallic substance capable of forming a lithium alloy is selected from the group consisting of Si, SiO x , Sn, SnOx, Ge, GeO x , Pb, PbO x , Ag, Mg, Zn, ZnO x , Ga, In, Sb, Bi, and alloys or composites thereof, in which x is a real number of 0.1-6.
8. The porous anode active material of claim 1 , wherein the crystalline carboneous substance is at least one selected from the group consisting of vapor grown carbon fibers (VGCFs), graphite, and carbon nanotubes (CNTs).
9. The porous anode active material of claim 1 , wherein a coating layer of the porous carboneous material consists of low-crystalline carbon having an interlayer spacing (d 002 ) of 3.45 Å or greater or amorphous carbon.
10. An anode comprising the porous anode active material of any one of claims 1 to 9 .
11. A lithium battery having an anode comprising the porous anode active material of any one of claims 1 to 9 .