Electroactive materials for metal-ion batteries
This invention relates to particulate electroactive materials comprising a plurality of composite particles, wherein the composite particles comprise: (a) a porous carbon framework including micropores and/or mesopores having a total volume of at least 0.7 cm 3 /g, wherein at least half of the micropore/mesopore volume is in the form of pores having a diameter of no more than 5 nm; and (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/or mesopores, wherein
the micropores and/or mesopores have a total pore volume as measured by gas adsorption of P 1 cm 3 /g, wherein P 1 has a value in the range from 0.7 to 1.4, and
the PD 50 pore diameter as measured by gas adsorption is no more than 4 nm;
the PD 90 pore diameter as measured by gas adsorption is no more than 15 nm; and
(b) a plurality of nanoscale 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 [0.5×P 1 to 1.3×P 1 ]:1;
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 total oxygen content of the composite particles is less than 10 wt %.
2 . A particulate material according to claim 1 , wherein P 1 is in the range from 0.75 to 1.3.
3 . A particulate material according to claim 1 , wherein the PD 50 pore diameter of the porous carbon framework is no more than 3 nm.
4 . A particulate material according to claim 1 , wherein the PD 7 O pore diameter of the porous carbon framework is no more than 5 nm.
5 . A particulate material according to claim 1 , wherein the PD 95 pore diameter of the porous carbon framework is no more than 20 nm.
6 . A particulate material according to claim 1 , wherein the weight ratio of silicon to the porous carbon framework is in the range from [0.5×P 1 to 1.2×P 1 ]:1.
7 . A particulate material according to claim 1 , wherein at least a portion of the micropores and/or mesopores comprise void space that is fully enclosed by the silicon.
8 . 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.
9 . A particulate material according to claim 1 , wherein the porous carbon framework is obtained by the pyrolysis of plant biomass, lignocellulosic materials and fossil carbon sources.
10 . A particulate material according to claim 1 , wherein Z is no more than 5%.
11 . A particulate material according to claim 1 , wherein the composite particles have a D 50 particle diameter of no more than 20 μm.
12 . 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 80 μm.
13 . A particulate material according to claim 1 , wherein the composite particles have a particle size distribution span of 5 or less.
14 . A particulate material according to claim 1 , wherein the composite particles have a BET surface area of no more than 150 m 2 /g.
15 . A particulate material according to claim 1 , having specific capacity on lithiation of 1200 to 2340 mAh/g.
16 . 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.
17 . An electrode comprising a particulate material according to claim 1 , in electrical contact with a current collector.
18 . A rechargeable metal-ion battery comprising:
(i) an anode, wherein the anode comprises an electrode according to claim 17 ;
(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.
19 . A particulate material comprising a plurality of composite particles, wherein the composite particles comprise:
(a) a porous carbon framework comprising micropores and/or mesopores, wherein
the micropores and/or mesopores have a total pore volume as measured by gas adsorption of P 1 cm 3 /g, wherein P 1 has a value of no more than 1.4, and
the PD 7 O pore diameter as measured by gas adsorption is no more than 5 nm; and
(b) a plurality of nanoscale 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 [0.5×P 1 to 1.3×P 1 ]:1;
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 particle size distribution span of 5 or less.
20 . A particulate material according to claim 19 , wherein the PD 7 O pore diameter as measured by gas adsorption is no more than 2 nm.
21 . A particulate material according to claim 19 , wherein the PD 50 pore diameter as measured by gas adsorption is no more than 2 nm, and Z is no more than 5%.
22 . A particulate material according to claim 19 , 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.