Surface-modified low surface area graphite, processes for making it, and applications of the same
Surface-modified, low surface area synthetic graphite may have a BET surface from 1.0 to 4.0 m 2 /g and a crystallite size L c to crystallite size L a ratio of greater than 1. Processes for modifying the surface of low surface area synthetic graphite may result in surface-modified, low surface area synthetic graphite have a BET surface from 1.0 to 4.0 m 2 /g and a crystallite size L c to crystallite size L a ratio of greater than 1. Such synthetic graphite may have many uses, including for example, as a negative electrode material in lithium-ion batteries.
1. Surface-modified synthetic graphite, wherein the surface-modified synthetic graphite:
has a BET surface area from about 1.0 to about 4 m 2 /g;
has a crystallite size L c (as measured by XRD) from 50 to 200 nm;
has a crystallite size L a (as measured by Raman spectroscopy) from 5 to 100 nm; and
exhibits a ratio (L c /L a ) of the perpendicular axis crystallite size L c (measured by XRD) to the parallel axis crystallite size L a (measured by Raman spectroscopy) of greater than 1.5.
2. The surface-modified synthetic graphite of claim 1 , further characterized by at least one of the following characteristics:
i) a BET surface area ranging from 1 to 3.5 m 2 /g;
ii) an ash content of below 0.04%;
iii) a particle size distribution (D90) ranging from 10 to 50 μm;
iv) a particle size distribution (D50) ranging from 5 to 40 μm;
v) an Fe content of below 20 ppm;
vi) an oxygen content of greater than 50 ppm; and
vii) a tapped density of greater than 0.8 g/cm 3 .
3. The surface-modified synthetic graphite of claim 1 , further characterized by at least one of the following characteristics:
i) a pH value ranging from 5.0 to 6.5;
ii) a xylene density from 2.24 to 2.26 g/cm 3 ; and
iii) exhibiting an ID/IG ratio (R(ID/IG)) of below about 0.3 when measured with a laser having excitation wavelength of 632.8 nm.
4. The surface-modified synthetic graphite of claim 3 , characterized by the following characteristics:
i) a BET surface ranging from 2.3 to 3 m 2 /g;
ii) a crystallite size L c ranging from 100 to 180 nm;
iii) a crystallite size L a ranging from 10 to 40 nm;
iv) a pH value ranging from 5.2 to 6.0;
v) an oxygen content of greater than 90 ppm;
vi) a tapped density of greater than 0.98 g/cm 3 ; and
vii) a particle size distribution (D90) ranging from 25 to 35 μm.
5. The surface-modified synthetic graphite of claim 3 , wherein the graphite is obtainable by oxidation of synthetic graphite with a BET surface area ranging from 1 m 2 /g to about 3.5 m 2 /g at temperatures from 500 to 1100° C. with treatment times ranging from 2 to 30 minutes.
6. Surface-modified synthetic graphite, wherein the surface-modified synthetic graphite:
has a BET surface area from about 1.0 to about 4 m 2 /g;
has a crystallite size L c (as measured by XRD) from 50 to 200 nm;
has a crystallite size L a (as measured by Raman spectroscopy) from 5 to 100 nm;
exhibits a ratio (L c /L a ) of the perpendicular axis crystallite size L c (measured by XRD) to the parallel axis crystallite size L a (measured by Raman spectroscopy) of greater than 1.5; and
has an oxygen content of greater than 50 ppm.
7. The surface-modified synthetic graphite of claim 6 , further characterized by at least one of the following characteristics:
i) a pH value ranging from 5.0 to 6.5;
ii) a xylene density from 2.24 to 2.26 g/cm 3 ; and
iii) exhibiting an ID/IG ratio (R(ID/IG)) of below about 0.3 when measured with a laser having excitation wavelength of 632.8 nm.
8. The surface-modified synthetic graphite of claim 6 , characterized by the following characteristics:
i) a BET surface ranging from 2.3 to 3 m 2 /g;
ii) a crystallite size L c ranging from 100 to 180 nm;
iii) a crystallite size L a ranging from 10 to 40 nm;
iv) a pH value ranging from 5.2 to 6.0;
v) an oxygen content of greater than 90 ppm;
vi) a tapped density of greater than 0.98 g/cm 3 ; and
vii) a particle size distribution (D90) ranging from 25 to 35 μm.
9. The surface-modified synthetic graphite of claim 6 , further characterized by at least one of the following characteristics:
i) a BET surface area ranging from 1 and 2 m 2 /g; and
ii) a xylene density ranging from 2.1 to 2.26 g/cm 3 .
10. The surface-modified synthetic graphite of claim 6 , wherein the surface-modified synthetic graphite is characterized by the following characteristics:
i) a BET surface area ranging from 1.3 to 1.8 g/cm 3 ;
ii) a crystallite size L c ranging from 100 to 160 nm; and
iii) a crystallite size L a ranging from 20 to 60 nm.
11. The surface-modified synthetic graphite of claim 6 , wherein said graphite is obtainable by chemical vapor deposition (CVD) on a synthetic graphite starting material at temperatures from 500 to 1000° C. with hydrocarbon gas and treatment times ranging from 3 to 120 minutes.
12. Surface-modified synthetic graphite, wherein the surface-modified synthetic graphite:
has a BET surface area from about 1.0 to about 4 m 2 /g;
has a crystallite size L c (as measured by XRD) from 50 to 200 nm;
has a crystallite size L a (as measured by Raman spectroscopy) from 5 to 100 nm;
exhibits a ratio (L c /L a ) of the perpendicular axis crystallite size L c (measured by XRD) to the parallel axis crystallite size L a (measured by Raman spectroscopy) of greater than 1.5; and
has a particle size distribution (D50) ranging from 5 to 40 μm.
13. The surface-modified synthetic graphite of claim 12 , further characterized by at least one of the following characteristics:
i) a pH value ranging from 5.0 to 6.5;
ii) a xylene density from 2.24 to 2.26 g/cm 3 ; and
iii) exhibiting an ID/IG ratio (R(ID/IG)) of below about 0.3 when measured with a laser having excitation wavelength of 632.8 nm.
14. The surface-modified synthetic graphite of claim 12 , characterized by the following characteristics:
i) a BET surface ranging from 2.3 to 3 m 2 /g;
ii) a crystallite size L c ranging from 100 to 180 nm;
iii) a crystallite size L a ranging from 10 to 40 nm;
iv) a pH value ranging from 5.2 to 6.0;
v) an oxygen content of greater than 90 ppm;
vi) a tapped density of greater than 0.98 g/cm 3 ; and
vii) a particle size distribution (D90) ranging from 25 to 35 μm.
15. The surface-modified synthetic graphite of claim 12 , further characterized by at least one of the following characteristics:
i) a BET surface area ranging from 1 and 2 m 2 /g; and
ii) a xylene density ranging from 2.1 to 2.26 g/cm 3 .
16. The surface-modified synthetic graphite of claim 12 , wherein the surface-modified synthetic graphite is characterized by the following characteristics:
i) a BET surface area ranging from 1.3 to 1.8 g/cm 3 ;
ii) a crystallite size L c ranging from 100 to 160 nm; and
iii) a crystallite size L a ranging from 20 to 60 nm.
17. The surface-modified synthetic graphite of claim 12 , wherein said graphite is obtainable by chemical vapor deposition (CVD) on a synthetic graphite starting material at temperatures from 500 to 1000° C. with hydrocarbon gas and treatment times ranging from 3 to 120 minutes.