US2014193711A1PendingUtilityA1

Combined electrochemical and chemical etching processes for generation of porous silicon particulates

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Assignee: BISWAL SIBANI LISAPriority: Jan 7, 2013Filed: Jan 7, 2014Published: Jul 10, 2014
Est. expiryJan 7, 2033(~6.5 yrs left)· nominal 20-yr term from priority
Inventors:Sibani Lisa BiswalMichael S. WongMadhuri ThakurSteven L. Sinsabaugh
H01M 4/134H01M 4/386H01M 10/0525H01M 4/622C01P 2006/16H01M 10/052Y02E60/10H01M 4/1395H01M 4/626C01B 33/02H01M 4/621H01M 2004/021C25F 3/12H01M 4/366C01P 2004/61Y02P20/133H01M 2004/027H01M 4/044
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Claims

Abstract

Embodiments of the present disclosure pertain to methods of preparing porous silicon particulates by: (a) electrochemically etching a silicon substrate, where electrochemical etching comprises exposure of the silicon substrate to an electric current density, and where electrochemical etching produces a porous silicon film over the silicon substrate; (b) separating the porous silicon film from the silicon substrate, where the separating comprises a gradual increase of the electric current density in sequential increments; (c) repeating steps (a) and (b) a plurality of times; (d) electrochemically etching the silicon substrate in accordance with step (a) to produce a porous silicon film over the silicon substrate; (e) chemically etching the porous silicon film and the silicon substrate; and (f) splitting the porous silicon film and the silicon substrate to form porous silicon particulates. Further embodiments of the present disclosure pertain to the formed porous silicon particulates and anode materials that contain them.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
         1 . A method of preparing porous silicon particulates, wherein the method comprises:
 (a) electrochemically etching a silicon substrate,
 wherein the electrochemical etching comprises exposure of the silicon substrate to an electric current density, and 
 wherein the electrochemical etching produces a porous silicon film over the silicon substrate; 
   (b) separating the porous silicon film from the silicon substrate,
 wherein the separating comprises a gradual increase of the electric current density in sequential increments; 
   (c) repeating steps (a) and (b) a plurality of times;   (d) electrochemically etching the silicon substrate in accordance with step (a) to produce a porous silicon film over the silicon substrate;   (e) chemically etching the porous silicon film and the silicon substrate; and   (f) splitting the porous silicon film and the silicon substrate to form porous silicon particulates.   
     
     
         2 . The method of  claim 1 , wherein the silicon substrate comprises a silicon wafer. 
     
     
         3 . The method of  claim 1 , wherein the electrochemical etching of the silicon substrate comprises use of an acid. 
     
     
         4 . The method of  claim 3 , wherein the acid comprises hydrofluoric acid. 
     
     
         5 . The method of  claim 1 , wherein the electrochemical etching comprises exposure of the silicon substrate to an electric current density of about 1 mA/cm 2  to about 10 mA/cm 2 . 
     
     
         6 . The method of  claim 1 , wherein the gradual increase of the electric current density during the separating step comprises an increase of the electric current density by about 1-2 mA/cm 2  per sequential increment. 
     
     
         7 . The method of  claim 1 , wherein steps (a) and (b) are repeated more than 5 times. 
     
     
         8 . The method of  claim 1 , wherein steps (a) and (b) are repeated until the porous silicon film becomes inseparable from the silicon substrate. 
     
     
         9 . The method of  claim 1 , wherein steps (a) and (b) are repeated until the silicon substrate develops one or more cracks. 
     
     
         10 . The method of  claim 1 , wherein the chemical etching occurs by exposure of the porous silicon film and the silicon substrate to a metal. 
     
     
         11 . The method of  claim 10 , wherein the metal is selected from the group consisting of silver, copper, chromium, gold, aluminum, tantalum, lead, zinc, silicon, and combinations thereof. 
     
     
         12 . The method of  claim 10 , wherein the metal is silver. 
     
     
         13 . The method of  claim 10 , wherein the exposure results in coating of the porous silicon film and the silicon substrate with the metal. 
     
     
         14 . The method of  claim 1 , wherein the splitting occurs by at least one of physical grinding, crushing, sonication, ultrasonication, ultrasonic fracture, pulverization, ultrasonic pulverization, and combinations thereof. 
     
     
         15 . The method of  claim 1 , wherein the splitting occurs by ultrasonication. 
     
     
         16 . The method of  claim 1 , further comprising a step of associating the porous silicon particulates with a binding material. 
     
     
         17 . The method of  claim 16 , wherein the binding material is selected from the group consisting of binders, carbon materials, polymers, metals, additives, carbohydrates, and combinations thereof. 
     
     
         18 . The method of  claim 16 , wherein the binding material comprises a polymer selected from the group consisting of polyacrylonitrile (PAN), pyrolyzed polyacrylonitrile (PPAN), polyvinyldiene difluoride (PVDF), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and combinations thereof. 
     
     
         19 . The method of  claim 16 , wherein the binding material is carbonized. 
     
     
         20 . The method of  claim 19 , wherein the binding material comprises a carbonized polyacrylonitrile. 
     
     
         21 . The method of  claim 1 , wherein the formed porous silicon particulates comprise a plurality of pores, wherein the plurality of pores comprise diameters between about 1 nanometer to about 5 micrometers. 
     
     
         22 . The method of  claim 1 , wherein the plurality of pores comprise diameters of at least about 50 nm, less than about 50 nm, less than about 2 nm, and combinations thereof. 
     
     
         23 . The method of  claim 1 , wherein the plurality of pores comprise hierarchical pores. 
     
     
         24 . The method of  claim 23 , wherein the hierarchical pores comprise micropores and mesopores within macropores. 
     
     
         25 . The method of  claim 1 , wherein the formed porous silicon particulates have thicknesses ranging from about 10 micrometers to about 200 micrometers. 
     
     
         26 . The method of  claim 1 , wherein the formed porous silicon particulates comprise pores that span at least 50% of a thickness of the porous silicon particulates. 
     
     
         27 . The method of  claim 1 , wherein the formed porous silicon particulates comprise pores that span an entire thickness of the porous silicon particulates. 
     
     
         28 . The method of  claim 1 , wherein the porous silicon particulates comprise diameters from about 1 μm to about 50 μm. 
     
     
         29 . The method of  claim 1 , further comprising a step of controlling a thickness of the porous silicon film. 
     
     
         30 . The method of  claim 29 , wherein the thickness of the porous silicon film is controlled by adjusting one or more parameters selected from the group consisting of electric current density during electrochemical etching, resistivity of the silicon substrate during electrochemical etching, concentration of electrolyte etchants used during electrochemical or chemical etching, temperature during electrochemical or chemical etching, and combinations thereof. 
     
     
         31 . An anode material comprising:
 porous silicon particulates,
 wherein the porous silicon particulates comprise a plurality of pores, wherein the plurality of pores comprise diameters between about 1 nanometer to about 5 micrometers; 
   a coating associated with the porous silicon particulates; and   a binding material associated with the porous silicon particulates, wherein the binding material is selected from the group consisting of binders, carbon materials, polymers, metals, additives, carbohydrates, and combinations thereof.   
     
     
         32 . The anode material of  claim 31 , wherein the coating comprises a metal coating. 
     
     
         33 . The anode material of  claim 32 , wherein the metal is selected from the group consisting of silver, copper, chromium, gold, aluminum, tantalum, lead, zinc, silicon, and combinations thereof. 
     
     
         34 . The anode material of  claim 32 , wherein the metal is silver. 
     
     
         35 . The anode material of  claim 31 , wherein the binding material comprises a polymer selected from the group consisting of polyacrylonitrile (PAN), pyrolyzed polyacrylonitrile (PPAN), polyvinylidene difluoride (PVDF), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and combinations thereof. 
     
     
         36 . The anode material of  claim 31 , wherein the binding material comprises carbonized polyacrylonitrile. 
     
     
         37 . The anode material of  claim 31 , wherein the plurality of pores comprise diameters of at least about 50 nm, less than about 50 nm, less than about 2 nm, and combinations thereof. 
     
     
         38 . The anode material of  claim 31 , wherein the plurality of pores comprise hierarchical pores. 
     
     
         39 . The anode material of  claim 31 , wherein the hierarchical pores comprise micropores and mesopores within macropores. 
     
     
         40 . The anode material of  claim 31 , wherein the porous silicon particulates have thicknesses ranging from about 10 micrometers to about 200 micrometers. 
     
     
         41 . The anode material of  claim 31 , wherein the porous silicon particulates comprise pores that span at least 50% of a thickness of the porous silicon particulates. 
     
     
         42 . The anode material of  claim 31 , wherein the porous silicon particulates comprise pores that span an entire thickness of the porous silicon particulates. 
     
     
         43 . The anode material of  claim 31 , wherein the porous silicon particulates comprise diameters from about 1 μm to about 50 μm. 
     
     
         44 . The anode material of  claim 31 , wherein the anode material has a discharge capacity of at least about 600 mAh/g over at least 50 cycles. 
     
     
         45 . The anode material of  claim 31 , wherein the anode material has a discharge capacity of at least about 1000 mAh/g over at least 50 cycles. 
     
     
         46 . The anode material of  claim 31 , wherein the anode material has a Coulombic efficiency of at least about 90% over at least 50 cycles. 
     
     
         47 . The anode material of  claim 31 , wherein the anode material is utilized as part of a lithium ion battery.

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