Method of fabricating structured particles composed of silicon or a silicon-based material and their use in lithium rechargeable batteries

Abstract

Pillared particles of silicon or silicon-comprising material and a method of fabricating the same are disclosed. These particles may be used to create both a composite anode structure with a polymer binder, a conductive additive and a metal foil current collector, and an electrode structure. The structure of the particles overcomes the problems of charge/discharge capacity loss.

1 . A particle comprising a particle core and a plurality of elongate structures coating one or more surfaces of the particle, each extending outwardly from the particle core from a first end to a second end, wherein each of the plurality of elongate structures is attached to the core at the first end of the elongate structure and the second end of the elongate structure is an unattached free end, and wherein the elongate structures are formed from silicon. 
     
     
         2 . A particle as claimed in  claim 1 , wherein the fraction of the surface area of the particle core occupied by the elongate structures is in the range of 0.10 to 0.50. 
     
     
         3 . A particle as claimed in  claim 2 , wherein the particle has a diameter of at least 0.5 μm and the elongate structures have an aspect ratio of greater than 20:1. 
     
     
         4 . A particle as claimed in  claim 1  wherein the particles have a first dimension in the range of 10 μm to 1 mm. 
     
     
         5 . A particle as claimed in  claim 1 , wherein the elongate structures have a diameter in the range of 0.08 to 0.70 microns. 
     
     
         6 . A particle as claimed in  claim 1  in which the elongate structures have a length from the first end to the second end in the range of 4 to 100 microns. 
     
     
         7 . A particle as claimed in  claim 1 , wherein the elongate structures are formed from n-type silicon, p-type silicon, or metallurgical grade silicon. 
     
     
         8 . A particle as claimed in  claim 1  wherein the elongate structures have a silicon purity of 90.00 to 99.95% by mass. 
     
     
         9 . A particle as claimed in  claim 1  in which the plurality of elongate structures coat one or more surfaces of each particle. 
     
     
         10 . A particle as claimed in  claim 1 , wherein in each of the plurality of discrete particles, the plurality of elongate structures extend over all the surfaces of the particle core. 
     
     
         11 . A particle as claimed in  claim 1 , wherein the elongate structures and the particle core are formed from the same material. 
     
     
         12 . A particle as claimed in  claim 1 , wherein
 the fraction of the surface area of the particle core occupied by the elongate structures is in the range of 0.10 to 0.50;   the elongate structures have an aspect ratio of greater than 20:1;   the elongate structures have a diameter in the range of 0.08 to 0.70 microns;   the elongate structures have a length from the first end to the second end in the range of 4 to 100 microns;   the elongate structures have a silicon purity of 90.00 to 99.95% by mass; and   the plurality of elongate structures coat one or more surfaces of each particle.   
     
     
         13 . A plurality of discrete particles as claimed in  claim 1 . 
     
     
         14 . A solvent-based slurry comprising a solvent and a plurality of discrete particles as claimed in  claim 1 . 
     
     
         15 . A porous composite structure for an electrode comprising a plurality of discrete particles, each discrete particle comprising a particle core and a plurality of elongate structures coating one or more surfaces of the particle, each extending outwardly from the particle core from a first end to a second end, wherein each of the plurality of elongate structures is attached to the core at the first end of the elongate structure, and wherein the elongate structures are formed from silicon; and a binder binding the particles into the composite structure. 
     
     
         16 . A porous composite structure as claimed in  claim 15 , further comprising an electronic additive bound into the composite structure by the binder. 
     
     
         17 . A porous composite structure according to  claim 16 , having a pore volume of 10-30%. 
     
     
         18 . An electrochemical cell comprising an anode and a cathode, the anode comprising a porous composite structure according to  claim 15  disposed against a current collector. 
     
     
         19 . A method of fabricating a porous composite structure according to  claim 15 , the method comprising providing a solvent-based slurry of the plurality of discrete particles and a binder; coating the slurry onto a surface; and evaporating the solvent to create the porous composite structure. 
     
     
         20 . A method of fabricating a plurality of discrete particles, each particle comprising a particle core and a plurality of elongate structures coating one or more surfaces of the particle, each extending outwardly from the particle core from a first end to a second end, wherein each of the plurality of elongate structures is attached to the core at the first end of the elongate structure and the second end of the elongate structure is an unattached free end, and wherein the elongate structures are formed from silicon, the method comprising providing a plurality of silicon particles, and etching the silicon particle to form the elongate structures. 
     
     
         21 . A method as claimed in  claim 20  in which the elongate structures are created by galvanic exchange etching.