Negative electrode material for lithium secondary battery, method for producing same, negative electrode for lithium secondary battery using same and lithium secondary battery
View Patent ↗A negative-electrode material is provided that can be produced at a low cost and yields a lithium secondary battery with an excellent balance of various battery characteristics even when used in high electrode densities. It has a graphite powder with a tap density of 0.80 g/cm 3 or higher and 1.35 g/cm 3 or lower, an amount of surface functional groups, O/C value, of 0 or larger and 0.01 or smaller, a BET specific surface area of 2.5 m 2 /g or larger and 70 m 2 /g or smaller, a Raman R value of 0.02 or larger and 0.05 or smaller.
1. A negative-electrode material for a lithium secondary battery, comprising a graphite powder (A) having
a tap density of 0.8 g/cm 3 to 1.35 g/cm 3 ,
an amount of surface functional groups, O/C value, of 0 to 0.01,
a ratio of volume-based 90% diameter to volume-based 10% diameter (d 90 /d 10 ) is 1.5 to 4.0,
a BET specific surface area of 2.5 m 2 /g to 7.0 m 2 /g, and
a Raman R value of 0.02 to 0.05,
wherein the amount of surface functional groups, O/C value, is an atomic concentration ratio O/C (atomic concentration of O/atomic concentration of C) obtained from peak areas of spectra of C1s and O1s according to X-ray photoelectron spectroscopy, and
the Raman R value is an intensity ratio R (R=I B /I A ) between the intensity I A of a peak P A of about 1580 cm −1 and the intensity I B of a peak P B of about 1360 cm −1 according to Raman spectroscopy;
wherein the graphite powder (A) is produced by heat-treating a graphite consisting essentially of natural graphite to a temperature of 1600° C. to 3200° C.
2. The negative-electrode material of claim 1 , wherein the volume-based average diameter of the graphite powder (A) is 10 μm to 50 μm.
3. The negative-electrode material of claim 1 , wherein the graphite powder (A) is produced by heat-treating a natural graphite which is a spheroidized graphite powder.
4. The negative-electrode material of claim 1 , wherein the graphite powder (A) is a graphitized form of a natural graphite in the shape of a sphere.
5. The negative-electrode material of claim 1 , wherein the graphite powder (A) has a degree of circularity of 0.90 or more.
6. The negative-electrode material of claim 1 , wherein the ratio of volume-based 90% diameter to volume-based 10% diameter (d 90 /d 10 ) is 2.5 to 2.7.
7. The negative-electrode material of claim 1 , wherein the Raman R value of the graphite powder (A) is 0.02 to 0.04.
8. The negative-electrode material of claim 1 , wherein the graphite powder (A) is produced by heat-treating natural graphite which is a flaky graphite.
9. The negative-electrode material of claim 1 , wherein the graphite powder (A) is produced by heat-treating natural graphite which is a vein graphite.