Process for preparing electroactive materials for metal-ion batteries
The disclosure relates to a process for preparing particulate materials having high electrochemical capacities that are suitable for use as anode active materials in rechargeable metal-ion batteries. In one aspect, the disclosure provides a process for preparing a particulate material comprising a plurality of composite particles. The process includes providing particulate porous carbon frameworks comprising micro pores and/or mesopores, wherein the porous carbon frameworks have a D 50 particle diameter of at least 20 μm; depositing an electroactive material selected from silicon and alloys thereof into the micropores and/or mesopores of the porous carbon frameworks using a chemical vapour infiltration process in a fluidised bed reactor, to provide intermediate particles; and comminuting the intermediate particles to provide said composite particles.
1. A process for preparing composite particles, the process comprising:
(a) providing particulate porous carbon frameworks comprising micropores and/or mesopores, wherein the porous carbon frameworks have a D 50 particle diameter of at least 20 μm;
(b) depositing an electroactive material selected from silicon, tin, aluminium, germanium and alloys thereof into the micropores and/or mesopores of the porous carbon frameworks using a chemical vapour infiltration process while the porous carbon frameworks are fluidized, to provide intermediate particles; and
(c) comminuting the intermediate particles to provide said composite particles.
2. The process according to claim 1 , further comprising transferring the intermediate particles into a comminuting device prior to step (c).
3. The process according to claim 1 , wherein the electroactive material is silicon.
4. The process according to claim 1 , wherein the intermediate particles and the composite particles comprise a plurality of nanoscale domains of an elemental form of the electroactive material located within the micropores and/or mesopores of the porous carbon frameworks.
5. The process according to claim 1 , wherein the chemical vapour infiltration process is performed at a temperature in the range from 200 to 1,250° C.
6. The process according to claim 1 , further comprising a step of cooling the intermediate particles to a temperature of below 100° C. before comminuting the intermediate particles.
7. The process according to claim 1 , further comprising a step of passivating the intermediate particles before comminuting the intermediate particles.
8. The process according to claim 1 , wherein the comminuting is performed by a jet mill.
9. The process according to claim 1 , wherein the step of comminuting the intermediate particles is performed in an inert gas or in an environment where the oxygen concentration is less than 10 vol % oxygen.
10. The process according to claim 1 , wherein the micropores and/or mesopores of the porous carbon frameworks have a total pore volume as measured by gas adsorption of P 1 cm 3 /g, wherein the value of P 1 is in the range from 0.4 to 2.5.
11. The process according to claim 1 , wherein the porous carbon frameworks have a D 50 particle diameter in the range from 60 to 150 μm.
12. The process according to claim 1 , wherein the porous carbon frameworks have D 50 particle diameter of at least 30 μm.
13. The process according to claim 1 , wherein the porous carbon frameworks have a D 50 particle diameter of no more than 1000 μm.
14. The process according to claim 1 , wherein the porous carbon frameworks have a Do particle diameter of at least 5 μm and a D 90 particle diameter of no more than 1,500 μm.
15. The process according to claim 1 , wherein the porous carbon frameworks have a BET surface area of at least 750 m 2 /g and no more than 4,000 m 2 /g.
16. The process according to claim 1 , wherein the porous carbon frameworks have a PD 50 pore diameter as measured by gas adsorption of no more than 5 nm.
17. The process according to claim 1 , wherein the composite particles have a D 50 particle diameter in the range from 0.5 to 20 μm.
18. The process according to claim 1 , wherein the composite particles have a Do particle diameter of at least 0.2 μm and a D 90 particle diameter of no more than 80 μm.
19. The process according to claim 1 , wherein the composite particles have a particle size distribution span of no more than 5.
20. The process according to claim 1 , wherein the electroactive material is silicon, wherein the pore volume of the composite particles is expressed as P 1 cm 3 /g, and wherein the weight ratio, for the composite particles, of silicon to the porous carbon framework in the composite particles is in the range from [0.5×P 1 to 2.2×P 1 ]:1.
21. The process according to claim 1 , wherein the electroactive material is silicon, and wherein the composite particles comprise 30 to 80 wt % silicon.
22. The process according to claim 1 , wherein the composite particles comprise no more than 15 wt % oxygen.
23. A particulate material comprising composite particles obtainable by the process according to claim 1 .