Structured particles
A powder comprising pillared particles for use as an active component of a metal ion battery, the pillared particles comprising a particle core and a plurality of pillars extending from the particle core, wherein the pillared particles are formed from a starting material powder wherein at least 10% of the total volume of the starting material powder is made up of starting material particles having a particle size of no more than 10 microns.
1. A powder comprising a plurality of pillared particles for use as an active component of a metal ion battery, the pillared particles comprising a particle core and a plurality of elongated structures extending from the particle core, wherein the elongated structures comprise at least one of silicon, tin, germanium and aluminium, wherein both the length to thickness (L:T) and width to thickness (W:T) aspect ratios of the particle core are at least 3:1, wherein the thickness T is taken to be the smallest of the 3 dimensions of the particle core, and wherein a BET value of the pillared particles is more than 5 m 2 /g, and wherein a BET/PMF ratio of the pillared particles is less than 3, wherein BET is expressed in m 2 /g and PMF=[(Total mass of pillars extending from the particle core)/(Total mass of pillared particle)]×100%.
2. The powder according to claim 1 , wherein the pillared particles comprise particles wherein at least one dimension of the particles is less than 10 microns.
3. The powder according to claim 1 , wherein at least 10% of a total volume of the powder is made up of particles having a particle size of no more than 10 microns.
4. The powder according to claim 1 , wherein the elongated structures are formed from a material that, in use, undergoes a volume expansion of at least 10% upon complete insertion into the material of the metal ions of the metal ion battery.
5. The powder according to claim 1 , wherein the elongated structures comprise silicon.
6. The powder according to claim 1 , wherein the elongated structures do not comprise carbon.
7. The powder according to claim 1 , wherein the particle core comprises an electroactive material selected from graphite, graphene, hard carbon, silicon, germanium, gallium, tin, aluminium, lead, indium, antimony, bismuth, oxides, nitrides or hydrides thereof, mixtures of these, mixtures or composite alloys containing these elements and chalcogenides and ceramics that are electrochemically active.
8. The powder according to claim 1 , wherein the core comprises silicon or carbon.
9. The powder according to claim 1 , wherein a volume of the elongated structures is at least 20% of a total volume of the plurality of particles.
10. The powder according to claim 1 , wherein a BET value of the pillared particles is more than 5 m 2 /g and is less than 200 m 2 /g.
11. The powder according to claim 1 , wherein an average elongated structure density of the elongated structures on the particle core is in a range of 10-80%.
12. The powder according to claim 1 , wherein a mean average elongated structure diameter is less than 80 nm.
13. The powder according to claim 1 , wherein opposing surfaces of the particles carry elongated structures.
14. The powder according to claim 13 , wherein an average length of the elongated structures is less than 5 microns.
15. The powder according to claim 1 , wherein only one of two opposing surfaces of the particles carries elongated structures.
16. The powder according to claim 1 , wherein particles are substantially discrete from one another.
17. A composition comprising a powder according to claim 1 , comprising at least one of:
(i) at least one further active component;
(ii) at least one conductive, non-active component;
(iii) a binder; and
(iv) a solvent.
18. The composition according to claim 17 , wherein the composition has a composite porosity, as a percentage of a total volume of the composite, that is at least a value given by a sum of the volume of elongated structures multiplied by 2 and a volume of particle cores multiplied by 1.2.
19. A method of forming the powder as defined in claim 1 comprising the step of etching particles of a starting material powder to form the pillared particles.
20. The method according to claim 19 , wherein at least 10% of a total volume of the starting material powder is made up of starting material particles having a particle size of no more than 10 microns.
21. The method according to claim 19 , wherein a mean average length of elongated structures is less than 5 microns.