Method of Forming Yolk-Shell-Structured Material

Abstract

A yolk-shell-structured material (16, 59, 59a, 74) is disclosed as including a plurality of silicon nano-particles (12, 54, 54a, 62) and a cavity (16, 60, 80, 84) enclosed by a micron-sized shell (18, 72) made of carbon nano-particles (14, 56, 58). A method of forming a yolk-shell-structured material with silicon nano-particles (12) and a cavity (16) enclosed by a micron-sized shell (18) made of carbon nano-particles (14) is disclosed as including (a) providing a micron-sized cornstarch core (10), (b) forming a layer of nano silicon-particle (12) on the cornstarch core (10), (c) forming a micron-sized shell (18) of carbon nano-particles (14) on the layer of nano silicon-particle (12), and (d) removing the cornstarch core (10) by heating.

1 . A method of forming a yolk-shell-structured material including a plurality of submicron-sized particles of a first material and at least one cavity enclosed by a micron-sized shell made of a second material which is different from said first material, including:
 (e) providing a micron-sized composite core made of at least a plurality of submicron-sized particles of said first material and a third material,   (f) forming at least a first layer of particles of said second material on said micron-sized composite core, and   (g) removing at least part of said third material of said core to form said cavity.   
     
     
         2 . A method according to  claim 1 , wherein said first material includes at least silicon nano-particles. 
     
     
         3 . A method according to  claim 1 , wherein said second material includes at least carbon atoms. 
     
     
         4 . A method according to  claim 1 , wherein said third material includes at least latex particles. 
     
     
         5 . A method according to  claim 1 , wherein said step (e) includes:
 (h) homogenizing said first material, said third material and a water soluble polymer to form a polymer dispersion,   (i) atomizing said polymer dispersion to form a plurality of polymer dispersion droplets, and   (j) drying said plurality of polymer dispersion droplets to form a plurality of dried particle composites.   
     
     
         6 . A method according to  claim 5 , wherein said polymer dispersion includes a latex-silicon-polymer dispersion with a plurality of latex particles, a plurality of silicon nano-particles and a water soluble polymer. 
     
     
         7 . A method according to  claim 6 , wherein, after said step (j), substantially each of said latex particles is coated with a number of said silicon nano-particles. 
     
     
         8 . A method according to  claim 7 , wherein, after said step (j), a plurality of said coated latex particles are grouped into a generally globe-like structure. 
     
     
         9 . A method according to  claim 7 , further including a step (k), after said step (j), of coating a layer of electrically-conductive carbon on said dried particle composites. 
     
     
         10 . A method according to  claim 9 , wherein said electrically-conductive carbon is of a size of substantially 40 nm. 
     
     
         11 . A method according to  claim 9 , wherein said layer of electrically-conductive carbon is poreless, porous or mesoporous. 
     
     
         12 . A method according to  claim 9 , further including a step ( 1 ), after said step (k), of removing at least part of said latex particles. 
     
     
         13 . A method according to  claim 12 , wherein said step ( 1 ) is carried out in air and at a temperature of up to 500° C. 
     
     
         14 . A method according to  claim 12 , further including a step (m), either prior to or after said step ( 1 ), of carbonizing said polymer. 
     
     
         15 . A method according to  claim 14 , wherein said step (m) is carried out in an inert gas, a reducing gas, or a mixture thereof, at a temperature of up to 3,000° C. 
     
     
         16 . A method according to  claim 15 , wherein said inert gas includes nitrogen, argon, helium, or a mixture thereof. 
     
     
         17 . A method according to  claim 15 , wherein said reducing gas includes hydrogen, carbon monoxide, or a mixture thereof. 
     
     
         18 . A method according to  claim 5 , wherein said first material includes at least a plurality of silicon nano-particles, a plurality of carbon nano-particles and a water soluble polymer. 
     
     
         19 . A method according to  claim 18 , wherein said water soluble polymer includes at least one of sodium carboxymethyl cellulose, polyvinyl alcohol and dextran. 
     
     
         20 . A method according to  claim 5 , wherein said third material includes at least a plurality of water insoluble microspheres. 
     
     
         21 . A method according to  claim 20 , wherein said water insoluble microspheres include at least one of polystyrene (PS) and polymethylmethacrylate (PMMA). 
     
     
         22 . A method according to  claim 18 , wherein said plurality of dried particle composites include a plurality of silicon nano-particles, a plurality of carbon nano-particles, a water soluble polymer and a plurality of water insoluble microspheres. 
     
     
         23 . A method according to  claim 18 , further including a step (n) of carbonizing said water soluble polymer.