Electroactive materials for metal-ion batteries
The invention relates to a particulate material comprising a plurality of composite particles, wherein the composite particles comprise: (a) a porous carbon framework comprising micropores and mesopores having a total pore volume of at least 0.6 cm 3 /g and no more than 2 cm 3 /g, where the volume fraction of micropores is in the range from 0.5 to 0.9 and the volume fraction of pores having a pore diameter no more than 10 nm is at least 0.75, and the porous carbon framework has a D 50 particle size of less than 20 μm; (b) silicon located within the micropores and/or mesopores of the porous carbon framework in a defined amount relative to the volume of the micropores and/or mesopores.
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 and no more than 2,
(ii) the volume fraction of micropores (φ a ) is in the range from 0.5 to 0.9, based on the total volume of micropores and mesopores;
(iii) the volume fraction of pores having a pore diameter no more than 10 nm (φ 10 ) 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 1.9×P 1 ]:1.
2. A particulate material according to claim 1 , wherein P 1 has a value of at least 0.65.
3. A particulate material according to claim 1 , wherein P 1 has a value of no more than 1.8.
4. A particulate material according to claim 1 , wherein the volume fraction of micropores (φ a ) is in the range from 0.5 to 0.85.
5. 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.
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 +1]×P 1 .
7. 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 +1.1]×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 weight ratio of silicon to the porous carbon framework in the composite particles is no more than the value given by [φ b +1.5]×P 1 .
10. 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 1.1×P 1 .
11. A particulate material according to claim 1 , wherein the volume fraction of pores having a pore diameter of no more than 10 nm (φ 10 ) is at least 0.75, 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 0.2×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.
17. A particulate material according to claim 1 , wherein the composite particles have a D 50 particle diameter of no more than 18 μm.
18. A particulate material according to claim 1 , wherein the composite particles have a D 10 particle diameter of at least 0.2 μm.
19. A particulate material according to claim 1 , wherein the composite particles have a D 90 particle diameter of no more than 40 μm.
20. 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 30 m 2 /g.
21. A particulate material according to claim 1 , wherein
P 1 has a value of at least 0.65 and no more than 1.8;
the volume fraction of micropores (φ a ) is in the range from 0.55 to 0.8; and
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 .
22. A particulate material according to claim 21 , 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.
23. A particulate material according to claim 1 , having specific capacity on lithiation of 1200 to 2340 mAh/g.
24. A composition comprising a particulate material as defined in claim 1 , and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) an additional particulate electroactive material.
25. A composition according to claim 24 , comprising from 1 to 20 wt % of the particulate material, based on the total dry weight of the composition.
26. A composition according to claim 24 , comprising from 10 to 98 wt % of the at least one additional particulate electroactive material, based on the total dry weight of the composition.
27. A composition according to claim 24 , wherein the at least one additional particulate electroactive material has a specific capacity on lithiation in the range from 100 to 600 mAh/g.
28. An electrode comprising a particulate material as defined in claim 1 electrical contact with a current collector.
29. A rechargeable metal-ion battery comprising:
(i) an anode, wherein the anode comprises an electrode as described in claim 28 ;
(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.