Electroactive materials for metal-ion batteries

1. A particulate material comprising a plurality of composite particles, wherein the composite particles comprise:

(a) a porous carbon framework comprising micropores and mesopores, wherein

(i) the micropores and mesopores have a total pore volume as measured by gas adsorption of P 1 cm 3 /g, wherein P 1 has a value of at least 0.6,

(ii) the volume fraction of micropores (φ a ) is in the range from 0.1 to 0.9, based on the total volume of micropores and mesopores;

(iii) the volume fraction of pores having a pore diameter of no more than 20 nm (φ 20 ) is at least 0.75, based on the total volume of micropores and mesopores, and

(iv) the porous carbon framework has a D 50 particle size of less than 20 μm;

(b) a plurality of nanoscale elemental silicon domains located within the micropores and/or mesopores of the porous carbon framework;

wherein

the weight ratio of silicon to the porous carbon framework in the composite particles is in the range from [1×P 1 to 2.2×P 1 ]:1; and

the particulate material has a Z value of no more than 10% as determined by TGA analysis in air, in which Z=1.875×[(M f −M 800 )/M f ]×100%, in which M f is the mass of the TGA sample at completion of oxidation and M 800 is the mass of the TGA sample at 800° C.

2. A particulate material according to claim 1 , wherein P 1 has a value of at least 0.7.

3. A particulate material according to claim 1 , wherein P 1 has a value of no more than 2.

4. A particulate material according to claim 1 , wherein the volume fraction of micropores (φ a ) is in the range from 0.45 to 0.85, based on the total volume of micropores and mesopores.

5. A particulate material according to claim 1 , wherein the volume fraction of micropores (φ a ) is in the range from 0.2 to 0.5, based on the total volume of micropores and mesopores.

6. A particulate material according to claim 1 , wherein the weight ratio of silicon to the porous carbon framework in the composite particles is at least the value given by [φ b +0.75]×P 1 , wherein φ b represents the volume fraction of mesopores, based on the total volume of micropores and mesopores.

7. A particulate material according to claim 6 , wherein the weight ratio of silicon to the porous carbon framework in the composite particles is at least the value given by [φ b +1]×P 1 .

8. A particulate material according to claim 1 , wherein the weight ratio of silicon to the porous carbon framework in the composite particles is no more than the value given by [φ b +1.6]×P 1 .

9. A particulate material according to claim 1 , wherein the volume fraction of micropores is in the range from 0.15 to 0.85, based on the total volume of micropores and mesopores; and the weight ratio of silicon to the porous carbon framework in the composite particles is at least 1.1×P 1 .

10. A particulate material according to claim 1 , wherein the volume fraction of micropores is in the range from 0.2 to 0.5, based on the total volume of micropores and mesopores; and the weight ratio of silicon to the porous carbon framework in the composite particles is at least 1.45×P 1 .

11. A particulate material according to claim 1 , wherein the volume fraction of pores having a pore diameter of no more than 20 nm (φ 20 ) is at least 0.8, based on the total volume of micropores and mesopores.

12. A particulate material according to claim 1 , wherein the volume fraction of pores having a pore diameter of no more than 5 nm (φ 5 ) is at least 0.7, based on the total volume of micropores and mesopores.

13. A particulate material according to claim 1 , wherein the porous carbon framework has a monomodal pore size distribution.

14. A particulate material according to claim 1 , wherein the porous carbon framework has a bimodal or multimodal pore size distribution.

15. A particulate material according to claim 1 , wherein the porous carbon framework comprises macropores having a diameter in the range from greater than 50 nm to 100 nm having a total volume P 2 cm 3 /g as measured by mercury porosimetry, wherein P 2 is no more than 0.1×P 1 .

16. A particulate material according to claim 1 , wherein the composite particles have a D 50 particle diameter of at least 0.5 μm and no more than 18 μm.

17. A particulate material according to claim 1 , wherein the composite particles have a D 10 particle diameter of at least 0.2 μm and a D 90 particle diameter of no more than 40 μm.

18. A particulate material according to claim 1 , wherein the composite particles have a BET surface area of at least 0.1 m 2 /g and no more than 150 m 2 /g.

19. A particulate material according to claim 1 , having specific capacity on lithiation of 1200 to 2340 mAh/g.

20. A particulate material according to claim 1 , wherein at least 90 wt % of the silicon mass in the composite particles is located within the internal pore volume of the porous carbon framework.

21. A particulate material according to claim 1 , wherein Z is no more than 5%.

22. A composition comprising a particulate material according to claim 1 , and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) an additional particulate electroactive material.

23. An electrode comprising a particulate material according to claim 1 in electrical contact with a current collector.

24. A rechargeable metal-ion battery comprising:

(i) an anode, wherein the anode comprises an electrode according to claim 23 ;

(ii) a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; and

(iii) an electrolyte between the anode and the cathode.

25. A particulate material comprising a plurality of composite particles, wherein the composite particles comprise:

(a) a porous carbon framework comprising micropores and mesopores, wherein

(i) the micropores and mesopores have a total pore volume as measured by gas adsorption of P 1 cm 3 /g, wherein P 1 has a value of at least 0.6,

(ii) the volume fraction of micropores (φ a ) is in the range from 0.45 to 0.9, based on the total volume of micropores and mesopores;

(iii) the volume fraction of pores having a pore diameter of no more than 20 nm (φ 20 ) is at least 0.85, based on the total volume of micropores and mesopores, and

(iv) the porous carbon framework has a D 50 particle size of less than 20 μm; and

(b) a plurality of nanoscale elemental silicon domains located within the micropores and/or mesopores of the porous carbon framework;

wherein

the weight ratio of silicon to the porous carbon framework in the composite particles is in the range from [1×P 1 to 2.2×P 1 ]:1;

wherein the particulate material has a Z value of no more than 10% as determined by TGA analysis in air, in which Z=1.875×[(M f −M 800 )/M f ]×100%, in which M f is the mass of the TGA sample at completion of oxidation and M 800 is the mass of the TGA sample at 800° C.; and

the composite particles have a BET surface area of no more than 30 m 2 /g.

26. A particulate material according to claim 25 , wherein the volume fraction of micropores (φ a ) is in the range from 0.6 to 0.85, based on the total volume of micropores and mesopores.

27. A particulate material according to claim 25 , wherein Z is no more than 5%.

28. A particulate material according to claim 25 , wherein:

the porous carbon framework comprises amorphous carbon;

the total volume of macropores in the porous carbon framework is P 2 cm 3 /g, wherein P 2 is no more than 0.1×P 1 ;

the silicon is amorphous silicon; and

the specific capacity of the particulate material on lithiation is 1200 to 2340 mAh/g.